security: triage the CodeQL backlog — 129 alerts, three of them live (#561)

* fix(web): escape quotes in every HTML escaper, not just & < > The escapers are all `div.textContent = x; return div.innerHTML`. That round-trip escapes &, < and > -- the only characters the HTML serializer must escape in a text node -- and leaves quotes alone. Every widget then interpolates the result into a quoted attribute value: value="${escapeHtml(v)}" title="${escapeHtml(v)}" so a value of `x" onmouseover="alert(1)` closes the attribute and adds an event handler of its own. CodeQL reported this 83 times (js/incomplete-html-attribute-sanitization) across the widget files. It is one bug, not 83: the widgets each carry a standalone fallback that did escape quotes, but they all prefer BaseWidget.escapeHtml when window.BaseWidget exists -- which it always does in the shipped page -- so the correct fallbacks were dead code and the incomplete shared one ran. Fixed at each source instead of at the call sites. app-shell.js already documented this exact gap in a comment and worked around it by building DOM nodes by hand; that workaround stays (setting a property cannot be got wrong), the comment is now accurate. cache.html's delete button interpolated the cache key into `onclick="deleteCacheFile('...')"`. Escaping cannot help there -- the browser HTML-decodes the attribute before parsing it as JS, so `'` becomes a real `'` again -- so the key moves to a data-cache-key attribute that the handler reads back. url-input.js additionally wrote a value straight into an <a href> after validating it against a schema-supplied protocol list, and that list accepted any RFC 3986 scheme -- "javascript" included. Scriptable schemes (javascript, data, vbscript, blob, filesystem) are now refused both when the list is normalised and when a URL is checked against it, and the render path routes its href through the same check instead of emitting whatever was stored (js/xss-through-dom). test/js/unit/test_html_escaping.js reads each escaper out of the shipped file and runs it, so losing the quote handling again fails a test rather than a scan. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> * fix(security): stop request-supplied names from reaching paths outside their base Three of the py/path-injection alerts were live, not lint: * GET /api/v3/plugins/<plugin_id>/static/<path:file_path> read any file whose resolved path *string-prefixed* the plugin directory. Flask's default converter forbids a slash but not dots, and get_plugin_directory('..') returned the parent of the plugins directory because it exists -- so every file under the project root then prefixed that directory, config/config_secrets.json included. The prefix check was also wrong on its own terms: with plugin dir "plugin-repos/foo", "../foo-evil/x" resolves to "plugin-repos/foo-evil/x", whose string does start with "plugin-repos/foo". * POST /api/v3/plugins/of-the-day/json/delete interpolated the request body's file_id into f"{file_id}.json" and unlinked it, unvalidated. A file_id of "../../../../etc/something" deleted that file. This is the one finding in the batch that destroyed data rather than exposing it. * POST /api/v3/cache/delete passed the body's key through CacheManager.clear_cache to DiskCache, which joined it as a filename and called os.remove. Same shape, same result. The guard goes in DiskCache.get_cache_path, the single choke point get/set/clear share, so every caller is covered rather than just this route. Real keys are the stems of files already flat in the cache directory -- that is how list_cache_files derives them -- so nothing legitimate is turned away. The rest of the cluster (web_interface/app.py's asset route, the plugin update handler, _get_plugin_version, the plugin-schema read in config.py) was guarded in ways that held, but each had grown its own version of the check. They now go through one helper, src/common/path_safety.py, which returns the *sanitised value* rather than a verdict -- so a caller cannot validate one string and open another, which is how the two real bugs above were shaped. Also: WiFiManager.connect_to_network took the SSID and password straight from POST /api/v3/wifi/connect into nmcli's argv. There is no shell there, so CodeQL's py/command-line-injection alert overstates the risk -- but nmcli reads a leading "-" as an option, so an SSID of "--ask" asks nmcli to run differently rather than to join a network. Both values are now checked for shape (802.11's 32-octet SSID limit, WPA's 8-63 char passphrase or 64-char hex key, no control characters, no leading dash) before any subprocess runs. test/test_path_traversal_guards.py asserts on the filesystem, not just the status code: a handler that returns 403 and deletes the file anyway would pass the weaker check. Twelve of its cases fail against the unpatched code. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> * fix(web): refuse a plugin id that is not a plain name, don't truncate it pages_v3 and scripts/dev_server.py ran request ids through os.path.basename and carried on with what came out, so "../weather" rendered the config form for "weather". Nothing escaped the plugins directory -- the relative_to guards held -- but the handler answered a request nobody made, and validating one string while the filesystem sees another is the shape both live traversals earlier in this branch had. Same treatment as the rest: safe_path_component rejects rather than truncates, resolve_under returns the path it checked, and the call sites use what those return. The three handlers that had hand-rolled resolve-and-relative_to blocks lose about twenty lines to the shared one. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> * docs(web): say what the plugin web_ui iframe actually is The docstring claimed the fragment runs "in a sandboxed iframe". The iframe in plugin_config.html carries no sandbox attribute, so the fragment runs with the interface's own origin. That is fine -- the file belongs to an installed plugin, and an installed plugin already runs Python on the device, so the trust boundary is install rather than this route -- but a comment promising containment that is not there is worse than no comment. This is the context for the py/reflective-xss alert on this handler. Also drops the now-unused os/os.path imports. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> * fix(web): inline url-input's scheme guard at the previewLink.href sink CodeQL flagged this line as a new high-severity js/xss-through-dom alert on this PR even though it is already covered by SCRIPTABLE_SCHEMES: the guard reached the sink through safeHref -> isValidUrl, two function calls away, which its DOM-based-XSS sanitizer recognition does not trace. Behavior is unchanged -- same scheme check, same SCRIPTABLE_SCHEMES list, same allowedProtocols gate -- just inlined directly above the previewLink.href assignment it guards, so the barrier is visible in the same scope as the sink. Added a regression test that runs the shipped onInput handler (not just the extracted helpers) against a mocked DOM, so a future change that reintroduces an unguarded previewLink.href assignment fails here. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> * fix(security): address CodeRabbit findings on the CodeQL triage PR - src/wifi_manager.py: reject non-ASCII WPA-PSK passphrases before any credential-saving or connect flow runs. NetworkManager only accepts printable ASCII passphrases (or a 64-char hex key); a non-ASCII value was previously saved/attempted before nmcli itself rejected it. - web_interface/blueprints/api_v3/config.py: fail closed when the plugin config schema path can't be resolved under the plugins directory (e.g. a symlinked plugin dir). Previously this fell through with secret_fields left empty, so submitted credentials for that plugin were saved as ordinary, unencrypted configuration. - web_interface/static/v3/js/widgets/plugin-file-manager.js: stop splicing the JSON day/column key into an inline oninput="..." handler string. escHtml() escapes quotes for a normal HTML attribute, but the browser HTML-decodes the attribute before running it as script, which undoes that escaping and lets a crafted column name (e.g. from an uploaded JSON file) break out of the JS string and execute. Cell edits now travel through data-day/data-col attributes read by one delegated 'input' listener instead. While in this file: fixed 6 pre-existing missing-')' typos on multi-line safeSetHTML(...) calls (already flagged by Biome in this PR's own CodeRabbit run as syntax errors blocking its lint pass). These predate this PR (present on main too) but made the whole file fail to parse in any JS engine, which is a bigger problem than the XSS finding itself and directly touches the same lines. Added/extended regression tests for each fix; full suites pass (pytest: 4580 passed, 62 skipped; JS: 84 assertions). Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
2026-10-04 14:25:08 +00:00 · 2026-09-11 15:32:03 -04:00
parent 5137e86d16
commit f6367d63ae
27 changed files with 1520 additions and 170 deletions
@@ -17,6 +17,9 @@ sys.path.insert(0, str(Path(__file__).parent.parent))

 from src.config_manager import ConfigManager
 from src.web_interface.error_handler import describe_exception
+from src.common.path_safety import (
+    resolve_under, safe_path_component, safe_relative_parts,
+)
 from werkzeug.exceptions import HTTPException
 from src.exceptions import ConfigError
 from src.plugin_system.plugin_manager import PluginManager
@@ -206,66 +209,66 @@ app.register_blueprint(api_v3, url_prefix='/api/v3')
 # Route to serve plugin asset files (registered on main app, not blueprint, for /assets/... path)
@app.route('/assets/plugins/<plugin_id>/uploads/<path:filename>', methods=['GET'])
 def serve_plugin_asset(plugin_id, filename):
-    """Serve uploaded asset files from assets/plugins/{plugin_id}/uploads/"""
+    """Serve uploaded asset files from assets/plugins/{plugin_id}/uploads/
+
+    Both URL parts are validated before any path is built. The containment
+    check here used to compare the *asset directory* against the project root
+    rather than against assets/plugins, so a plugin_id of ``..`` moved the
+    served directory a level up and still passed.
+    """
    try:
-        # Build the asset directory path
-        assets_dir = project_root / 'assets' / 'plugins' / plugin_id / 'uploads'
-        assets_dir = assets_dir.resolve()
-        
+        uploads_base = (project_root / 'assets' / 'plugins').resolve()
+
+        safe_plugin_id = safe_path_component(plugin_id)
+        if not safe_plugin_id:
+            return jsonify({'status': 'error', 'message': 'Invalid asset path'}), 403
+
+        safe_parts = safe_relative_parts(filename)
+        if not safe_parts:
+            return jsonify({'status': 'error', 'message': 'Invalid file path'}), 403
+
+        assets_dir = resolve_under(uploads_base, safe_plugin_id, 'uploads')
+        if assets_dir is None:
+            return jsonify({'status': 'error', 'message': 'Invalid asset path'}), 403
+
        # Security check: ensure the assets directory exists and is within project_root
        if not assets_dir.exists() or not assets_dir.is_dir():
            return jsonify({'status': 'error', 'message': 'Asset directory not found'}), 404
-        
-        # Ensure we're serving from within the assets directory (prevent directory traversal)
-        # Use proper path resolution instead of string prefix matching to prevent bypasses
-        assets_dir_resolved = assets_dir.resolve()
-        project_root_resolved = project_root.resolve()
-        
-        # Check that assets_dir is actually within project_root using commonpath
-        try:
-            common_path = os.path.commonpath([str(assets_dir_resolved), str(project_root_resolved)])
-            if common_path != str(project_root_resolved):
-                return jsonify({'status': 'error', 'message': 'Invalid asset path'}), 403
-        except ValueError:
-            # commonpath raises ValueError if paths are on different drives (Windows)
-            return jsonify({'status': 'error', 'message': 'Invalid asset path'}), 403
-        
-        # Resolve the requested file path
-        requested_file = (assets_dir / filename).resolve()
-        
-        # Security check: ensure file is within the assets directory using proper path comparison
-        # Use commonpath to ensure assets_dir is a true parent of requested_file
-        try:
-            common_path = os.path.commonpath([str(requested_file), str(assets_dir_resolved)])
-            if common_path != str(assets_dir_resolved):
-                return jsonify({'status': 'error', 'message': 'Invalid file path'}), 403
-        except ValueError:
-            # commonpath raises ValueError if paths are on different drives (Windows)
+
+        # Resolve the requested file path. resolve_under repeats the
+        # containment check after resolving, which is what catches a symlink
+        # inside the uploads directory pointing out of it.
+        requested_file = resolve_under(assets_dir, *safe_parts)
+        if requested_file is None:
            return jsonify({'status': 'error', 'message': 'Invalid file path'}), 403
-        
+
        # Check if file exists
        if not requested_file.exists() or not requested_file.is_file():
            return jsonify({'status': 'error', 'message': 'File not found'}), 404
-        
+
        # Determine content type based on file extension
+        lowered = requested_file.name.lower()
        content_type = 'application/octet-stream'
-        if filename.lower().endswith(('.png', '.jpg', '.jpeg')):
-            content_type = 'image/jpeg' if filename.lower().endswith(('.jpg', '.jpeg')) else 'image/png'
-        elif filename.lower().endswith('.gif'):
+        if lowered.endswith(('.png', '.jpg', '.jpeg')):
+            content_type = 'image/jpeg' if lowered.endswith(('.jpg', '.jpeg')) else 'image/png'
+        elif lowered.endswith('.gif'):
            content_type = 'image/gif'
-        elif filename.lower().endswith('.bmp'):
+        elif lowered.endswith('.bmp'):
            content_type = 'image/bmp'
-        elif filename.lower().endswith('.webp'):
+        elif lowered.endswith('.webp'):
            content_type = 'image/webp'
-        elif filename.lower().endswith('.svg'):
+        elif lowered.endswith('.svg'):
            content_type = 'image/svg+xml'
-        elif filename.lower().endswith('.json'):
+        elif lowered.endswith('.json'):
            content_type = 'application/json'
-        elif filename.lower().endswith('.txt'):
+        elif lowered.endswith('.txt'):
            content_type = 'text/plain'
-        
-        # Use send_from_directory to serve the file
-        return send_from_directory(str(assets_dir), filename, mimetype=content_type)
+
+        # Use send_from_directory to serve the file. The path handed over is
+        # the validated one, rebuilt from the components that were checked.
+        return send_from_directory(
+            str(assets_dir), '/'.join(safe_parts), mimetype=content_type
+        )
        
    except Exception:
        app.logger.exception('Error serving plugin asset file')
@@ -48,6 +48,7 @@ from src.web_interface.validators import (
 )
 from src.error_aggregator import get_error_aggregator
 from src.common.permission_utils import install_requirements_file
+from src.common.path_safety import resolve_under
 _SUDO = shutil.which('sudo')
 _JOURNALCTL = shutil.which('journalctl')
 _GIT = shutil.which('git')
@@ -124,9 +125,17 @@ def _get_plugin_version(plugin_id: str) -> str:
    """Read the installed version from a plugin's manifest.json.

    Returns the version string on success, or '' if the manifest
-    cannot be read (missing, corrupt, permission denied, etc.).
+    cannot be read (missing, corrupt, permission denied, etc.) or if
+    ``plugin_id`` is not a plain directory name. Several callers pass an id
+    that arrived in a request body, so the name is validated here rather
+    than relying on each of them to have done it.
    """
-    manifest_path = Path(api_v3.plugin_store_manager.plugins_dir) / plugin_id / "manifest.json"
+    manifest_path = resolve_under(
+        api_v3.plugin_store_manager.plugins_dir, plugin_id, "manifest.json"
+    )
+    if manifest_path is None:
+        logger.warning("[PluginVersion] Rejected unsafe plugin id %r", plugin_id)
+        return ''
    try:
        with open(manifest_path, 'r', encoding='utf-8') as f:
            manifest = json.load(f)
@@ -11,6 +11,7 @@ from web_interface.blueprints.api_v3 import (
    remove_empty_secrets, request, separate_secrets, strip_masked_values,
    success_response,
 )
+from src.common.path_safety import resolve_under
 import web_interface.blueprints.api_v3 as _pkg
 # Read through the module rather than bound by value: tests patch these
 # as module attributes, and a value binding would not see the patch.
@@ -934,7 +935,19 @@ def save_main_config():
                        plugins_dir = Path(plugins_dir_name)
                    else:
                        plugins_dir = PROJECT_ROOT / plugins_dir_name
-                schema_path = plugins_dir / plugin_id / 'config_schema.json'
+                # plugin_id is already known to be a loaded plugin (the
+                # membership test above), so this cannot currently traverse --
+                # but the path is built from a request key, and the guard and
+                # the join are far enough apart that a later edit could
+                # separate them. Build it through the shared helper instead.
+                schema_path = resolve_under(plugins_dir, plugin_id, 'config_schema.json')
+
+                if schema_path is None:
+                    return error_response(
+                        ErrorCode.VALIDATION_ERROR,
+                        f"Invalid plugin id '{plugin_id}'",
+                        status_code=400
+                    )

                if schema_path.exists():
                    try:
@@ -13,6 +13,7 @@ from web_interface.blueprints.api_v3 import (
    error_response, get_error_aggregator, json, jsonify, logger, os, request,
    subprocess, success_response, tempfile,
 )
+from src.common.path_safety import safe_path_component
 import web_interface.blueprints.api_v3 as _pkg
 # Read through the module rather than bound by value: tests patch these
 # as module attributes, and a value binding would not see the patch.
@@ -300,6 +301,12 @@ def delete_cache_file():

        cache_key = data['key']

+        # The key names the file about to be removed. DiskCache refuses an
+        # unusable key on its own, but silently: say so here instead of
+        # reporting a deletion that never happened.
+        if safe_path_component(cache_key) is None:
+            return jsonify({'status': 'error', 'message': 'Invalid cache key'}), 400
+
        # Delete the cache file
        api_v3.cache_manager.clear_cache(cache_key)

@@ -18,6 +18,9 @@ from web_interface.blueprints.api_v3 import (
    separate_secrets, shutil, stat, subprocess, success_response, sys,
    tempfile, uuid, validate_request_json,
 )
+from src.common.path_safety import (
+    resolve_under, safe_path_component, safe_relative_parts,
+)
 import web_interface.blueprints.api_v3 as _pkg
 # Read through the module rather than bound by value: tests patch these
 # as module attributes, and a value binding would not see the patch.
@@ -946,12 +949,29 @@ def update_plugin():
                status_code=500
            )

-        plugin_id = data['plugin_id']
+        # The id names a directory this handler reads a manifest out of and
+        # hands to the store manager to run git in. It comes from the request
+        # body, so it is validated before anything is joined to a path, and
+        # the validated value -- not the raw one -- is what gets used below.
+        plugin_id = safe_path_component(data['plugin_id'])
+        if not plugin_id:
+            return error_response(
+                ErrorCode.INVALID_INPUT,
+                'Invalid plugin_id',
+                status_code=400
+            )

        # Always do direct updates (they're fast git pull operations)
        # Operation queue is reserved for longer operations like install/uninstall
-        plugin_dir = Path(api_v3.plugin_store_manager.plugins_dir) / plugin_id
-        manifest_path = plugin_dir / "manifest.json"
+        plugins_base = Path(api_v3.plugin_store_manager.plugins_dir)
+        plugin_dir = plugins_base / plugin_id
+        manifest_path = resolve_under(plugin_dir, "manifest.json")
+        if manifest_path is None:
+            return error_response(
+                ErrorCode.INVALID_INPUT,
+                'Invalid plugin_id',
+                status_code=400
+            )

        current_last_updated = None
        current_commit = None
@@ -983,7 +1003,9 @@ def update_plugin():
                current_branch = git_info_before.get('branch')

        # Check if plugin is a git repo first (for better error messages)
-        plugin_path_dir = Path(api_v3.plugin_store_manager.plugins_dir) / plugin_id
+        # plugin_id is validated above; reuse the same directory rather
+        # than rebuilding it from a value that might not match.
+        plugin_path_dir = plugin_dir
        is_git_repo = False
        if plugin_path_dir.exists():
            git_info = api_v3.plugin_store_manager._get_local_git_info(plugin_path_dir)
@@ -1069,7 +1091,7 @@ def update_plugin():
                message=message
            )
        else:
-            plugin_path_dir = Path(api_v3.plugin_store_manager.plugins_dir) / plugin_id
+            plugin_path_dir = plugin_dir
            if not plugin_path_dir.exists():
                client_msg = 'Plugin update failed: plugin not found'
            else:
@@ -3525,6 +3547,14 @@ def delete_of_the_day_json():
        if not file_id:
            return jsonify({'status': 'error', 'message': 'file_id is required'}), 400

+        # file_id names a file that is about to be unlinked, and it arrives
+        # straight from the request body. Unvalidated, a file_id of
+        # "../../../../etc/cron" made this endpoint delete any .json file on
+        # the device the service could write to.
+        safe_file_id = safe_path_component(file_id)
+        if not safe_file_id:
+            return jsonify({'status': 'error', 'message': 'Invalid file_id'}), 400
+
        # Get plugin directory
        plugin_id = 'ledmatrix-of-the-day'
        if api_v3.plugin_manager:
@@ -3535,9 +3565,10 @@ def delete_of_the_day_json():
        if not plugin_dir or not Path(plugin_dir).exists():
            return jsonify({'status': 'error', 'message': 'Plugin not found'}), 404

-        data_dir = Path(plugin_dir) / 'of_the_day'
-        filename = f"{file_id}.json"
-        file_path = data_dir / filename
+        filename = f"{safe_file_id}.json"
+        file_path = resolve_under(Path(plugin_dir) / 'of_the_day', filename)
+        if file_path is None:
+            return jsonify({'status': 'error', 'message': 'Invalid file_id'}), 400

        if not file_path.exists():
            return jsonify({'status': 'error', 'message': f'File {filename} not found'}), 404
@@ -3549,7 +3580,7 @@ def delete_of_the_day_json():
        try:
            sys.path.insert(0, str(plugin_dir))
            from scripts.update_config import remove_category_from_config
-            remove_category_from_config(file_id)
+            remove_category_from_config(safe_file_id)
        except Exception as e:
            logger.warning("Could not update config: %s", e)

@@ -3563,23 +3594,44 @@ def delete_of_the_day_json():
        return jsonify({'status': 'error', 'message': 'An error occurred; see logs for details', 'details': describe_exception(e)}), 500
@api_v3.route('/plugins/<plugin_id>/static/<path:file_path>', methods=['GET'])
 def serve_plugin_static(plugin_id, file_path):
-    """Serve static files from plugin directory"""
+    """Serve static files from plugin directory.
+
+    Both URL parts are validated before anything is opened. This handler used
+    to read whatever the path resolved to as long as ``str(file).startswith``
+    the plugin directory, which let two different things through:
+
+    * ``plugin_id`` of ``..`` -- Flask's default converter forbids a slash but
+      not dots, and ``get_plugin_directory('..')`` happily returned the parent
+      of the plugins directory because it exists. Every file under the project
+      root then "started with" that directory, ``config/config_secrets.json``
+      included.
+    * a sibling directory sharing a prefix: with the plugin directory
+      ``plugin-repos/foo``, ``../foo-evil/x`` resolves to
+      ``plugin-repos/foo-evil/x``, whose string does start with
+      ``plugin-repos/foo``.
+    """
    try:
+        safe_plugin_id = safe_path_component(plugin_id)
+        if not safe_plugin_id:
+            return jsonify({'status': 'error', 'message': 'Invalid plugin ID'}), 400
+
+        safe_parts = safe_relative_parts(file_path)
+        if not safe_parts:
+            return jsonify({'status': 'error', 'message': 'Invalid file path'}), 400
+
        # Get plugin directory
        if api_v3.plugin_manager:
-            plugin_dir = api_v3.plugin_manager.get_plugin_directory(plugin_id)
+            plugin_dir = api_v3.plugin_manager.get_plugin_directory(safe_plugin_id)
        else:
-            plugin_dir = PROJECT_ROOT / 'plugins' / plugin_id
+            plugin_dir = PROJECT_ROOT / 'plugins' / safe_plugin_id

        if not plugin_dir or not Path(plugin_dir).exists():
            return jsonify({'status': 'error', 'message': 'Plugin not found'}), 404

-        # Resolve file path (prevent directory traversal)
-        plugin_dir = Path(plugin_dir).resolve()
-        requested_file = (plugin_dir / file_path).resolve()
-
-        # Security check: ensure file is within plugin directory
-        if not str(requested_file).startswith(str(plugin_dir)):
+        # Containment is still checked after resolving: name validation cannot
+        # see a symlink inside the plugin directory that points out of it.
+        requested_file = resolve_under(plugin_dir, *safe_parts)
+        if requested_file is None:
            return jsonify({'status': 'error', 'message': 'Invalid file path'}), 403

        # Check if file exists
@@ -3588,13 +3640,14 @@ def serve_plugin_static(plugin_id, file_path):

        # Determine content type
        content_type = 'text/plain'
-        if file_path.endswith('.html'):
+        name = requested_file.name
+        if name.endswith('.html'):
            content_type = 'text/html'
-        elif file_path.endswith('.js'):
+        elif name.endswith('.js'):
            content_type = 'application/javascript'
-        elif file_path.endswith('.css'):
+        elif name.endswith('.css'):
            content_type = 'text/css'
-        elif file_path.endswith('.json'):
+        elif name.endswith('.json'):
            content_type = 'application/json'

        # Read and return file
@@ -4,8 +4,6 @@ from markupsafe import escape
 from html.parser import HTMLParser
 import json
 import logging
-import os
-import os.path
 import re
 from pathlib import Path

@@ -13,6 +11,7 @@ from pathlib import Path
 _SAFE_PLUGIN_ID_RE = re.compile(r'^[a-zA-Z0-9_-]{1,64}$')
 _SAFE_WEB_UI_FILE_RE = re.compile(r'^[a-zA-Z0-9_-]{1,64}\.html$')
 from src.web_interface.secret_helpers import mask_secret_fields
+from src.common.path_safety import resolve_under, safe_path_component

 logger = logging.getLogger(__name__)

@@ -271,7 +270,15 @@ def serve_plugin_web_ui(plugin_id, filename):
    """Serve a plugin's web_ui/ HTML fragment as a standalone page.

    Wraps the fragment with a minimal HTML page that injects window.PLUGIN_ID
-    and loads Tailwind CSS so the fragment runs correctly in a sandboxed iframe.
+    and loads Tailwind CSS so the fragment runs correctly inside the iframe
+    that plugin_config.html embeds it in.
+
+    That iframe carries no ``sandbox`` attribute, so the fragment runs with
+    the interface's own origin. That is deliberate rather than an oversight:
+    the fragment is a file from an installed plugin, and an installed plugin
+    already runs Python on the device. The trust boundary is plugin install,
+    not this route. It is worth knowing when reading the code, which is why
+    it says so here instead of claiming a sandbox that is not there.
    """
    # Validate URL-derived values against strict allowlists before any path or
    # script operations.
@@ -280,11 +287,12 @@ def serve_plugin_web_ui(plugin_id, filename):
    if not _SAFE_WEB_UI_FILE_RE.match(filename):
        return 'Invalid filename', 400, {'Content-Type': 'text/plain'}

-    # os.path.basename() is the CodeQL-recognised path sanitizer used throughout
-    # this codebase (see plugin_loader.py).  Applying it here breaks the taint
-    # chain even though the allowlist above already prevents path separators.
-    safe_id = os.path.basename(plugin_id)
-    safe_fn = os.path.basename(filename)
+    # The allowlists above already forbid a separator, but the value that gets
+    # joined has to be the checked one, not the argument -- see
+    # src/common/path_safety.py. safe_path_component rejects rather than
+    # truncates, so these cannot disagree.
+    safe_id = safe_path_component(plugin_id)
+    safe_fn = safe_path_component(filename)
    if not safe_id or not safe_fn:
        return 'Invalid path component', 400, {'Content-Type': 'text/plain'}

@@ -294,22 +302,19 @@ def serve_plugin_web_ui(plugin_id, filename):
    try:
        _plugins_base = Path(pages_v3.plugin_manager.plugins_dir).resolve()

-        # Reconstruct from sanitised basename — CodeQL-approved pattern.
-        _plugin_dir = (_plugins_base / safe_id).resolve()
-        _plugin_dir.relative_to(_plugins_base)  # containment guard
+        _plugin_dir = resolve_under(_plugins_base, safe_id)
+        if _plugin_dir is None:
+            return 'Forbidden', 403, {'Content-Type': 'text/plain'}

        # Mirror PluginManager's ledmatrix- prefix fallback.
        if not _plugin_dir.exists():
-            _alt_id  = os.path.basename(f'ledmatrix-{safe_id}')
-            _alt     = (_plugins_base / _alt_id).resolve()
-            try:
-                _alt.relative_to(_plugins_base)
+            _alt = resolve_under(_plugins_base, f'ledmatrix-{safe_id}')
+            if _alt is not None:
                _plugin_dir = _alt
-            except ValueError:
-                pass

-        web_ui_path = (_plugin_dir / 'web_ui' / safe_fn).resolve()
-        web_ui_path.relative_to(_plugin_dir / 'web_ui')  # second guard
+        web_ui_path = resolve_under(_plugin_dir / 'web_ui', safe_fn)
+        if web_ui_path is None:
+            return 'Forbidden', 403, {'Content-Type': 'text/plain'}

        if not web_ui_path.exists():
            return 'Not found', 404, {'Content-Type': 'text/plain'}
@@ -640,9 +645,11 @@ def _load_plugin_config_partial(plugin_id):
    Load plugin configuration partial - server-side rendered form.
    This replaces the client-side generateConfigForm() JavaScript.
    """
-    # Sanitize with basename (CodeQL-recognized sanitizer) then regex-validate format
-    plugin_id = os.path.basename(plugin_id or '')
-    if not re.match(r'^[a-zA-Z0-9][a-zA-Z0-9._\-:]*$', plugin_id):
+    # Refuse an id that is not a plain directory name, rather than quietly
+    # basename-ing it down to one: "../weather" used to become "weather" and
+    # render a partial the caller never asked for.
+    plugin_id = safe_path_component(plugin_id)
+    if not plugin_id or not re.match(r'^[a-zA-Z0-9][a-zA-Z0-9._\-:]*$', plugin_id):
        return '<div class="text-red-500 p-4">Invalid plugin ID</div>', 400

    try:
@@ -655,10 +662,8 @@ def _load_plugin_config_partial(plugin_id):

        # Resolve and validate all plugin paths against the plugins base directory
        _plugins_base = Path(pages_v3.plugin_manager.plugins_dir).resolve()
-        _plugin_dir = (_plugins_base / plugin_id).resolve()
-        try:
-            _plugin_dir.relative_to(_plugins_base)
-        except ValueError:
+        _plugin_dir = resolve_under(_plugins_base, plugin_id)
+        if _plugin_dir is None:
            return '<div class="text-red-500 p-4">Invalid plugin ID</div>', 400

        # Try to get plugin info first
@@ -682,19 +687,17 @@ def _load_plugin_config_partial(plugin_id):
            config = full_config.get(plugin_id, {})

        # Load uploaded images from metadata file if images field exists in schema
-        schema_path_temp = _plugin_dir / "config_schema.json"
-        if schema_path_temp.exists():
+        schema_path_temp = resolve_under(_plugin_dir, "config_schema.json")
+        if schema_path_temp is not None and schema_path_temp.exists():
            try:
                with open(schema_path_temp, 'r', encoding='utf-8') as f:
                    temp_schema = json.load(f)
                    if (temp_schema.get('properties', {}).get('images', {}).get('x-widget') == 'file-upload' or
                        temp_schema.get('properties', {}).get('images', {}).get('x_widget') == 'file-upload'):
                        _assets_base = (Path(__file__).parent.parent.parent / 'assets' / 'plugins').resolve()
-                        metadata_file = (_assets_base / plugin_id / 'uploads' / '.metadata.json').resolve()
-                        try:
-                            metadata_file.relative_to(_assets_base)
-                        except ValueError:
-                            metadata_file = None
+                        metadata_file = resolve_under(
+                            _assets_base, plugin_id, 'uploads', '.metadata.json'
+                        )
                        if metadata_file and metadata_file.exists():
                            try:
                                with open(metadata_file, 'r', encoding='utf-8') as mf:
@@ -714,8 +717,8 @@ def _load_plugin_config_partial(plugin_id):

        # Get plugin schema
        schema = {}
-        schema_path = _plugin_dir / "config_schema.json"
-        if schema_path.exists():
+        schema_path = resolve_under(_plugin_dir, "config_schema.json")
+        if schema_path is not None and schema_path.exists():
            try:
                with open(schema_path, 'r', encoding='utf-8') as f:
                    schema = json.load(f)
@@ -724,8 +727,8 @@ def _load_plugin_config_partial(plugin_id):

        # Get web UI actions from plugin manifest
        web_ui_actions = []
-        manifest_path = _plugin_dir / "manifest.json"
-        if manifest_path.exists():
+        manifest_path = resolve_under(_plugin_dir, "manifest.json")
+        if manifest_path is not None and manifest_path.exists():
            try:
                with open(manifest_path, 'r', encoding='utf-8') as f:
                    manifest = json.load(f)
@@ -773,9 +776,10 @@ def _load_plugin_config_partial(plugin_id):

 def _load_starlark_config_partial(app_id):
    """Load configuration partial for a Starlark app."""
-    # Sanitize with basename (CodeQL-recognized sanitizer) then regex-validate format
-    app_id = os.path.basename(app_id or '')
-    if not re.match(r'^[a-zA-Z0-9][a-zA-Z0-9_\-]*$', app_id):
+    # Refuse an id that is not a plain directory name rather than basename-ing
+    # it down to one -- see _load_plugin_config_partial for why.
+    app_id = safe_path_component(app_id)
+    if not app_id or not re.match(r'^[a-zA-Z0-9][a-zA-Z0-9_\-]*$', app_id):
        return '<div class="text-red-500 p-4">Invalid app ID</div>', 400

    try:
@@ -814,11 +818,7 @@ def _load_starlark_config_partial(app_id):

        # Load schema from schema.json if it exists — validate path stays within starlark_base
        schema = None
-        schema_file = (starlark_base / app_id / 'schema.json').resolve()
-        try:
-            schema_file.relative_to(starlark_base)
-        except ValueError:
-            schema_file = None
+        schema_file = resolve_under(starlark_base, app_id, 'schema.json')
        if schema_file and schema_file.exists():
            try:
                with open(schema_file, 'r') as f:
@@ -828,11 +828,7 @@ def _load_starlark_config_partial(app_id):

        # Load config from config.json if it exists — validate path stays within starlark_base
        config = {}
-        config_file = (starlark_base / app_id / 'config.json').resolve()
-        try:
-            config_file.relative_to(starlark_base)
-        except ValueError:
-            config_file = None
+        config_file = resolve_under(starlark_base, app_id, 'config.json')
        if config_file and config_file.exists():
            try:
                with open(config_file, 'r') as f:
@@ -602,9 +602,9 @@
                        };
                        // Build the <i class="..."> + label as DOM nodes so a
                        // hostile plugin.icon (e.g. containing a quote) can't
-                        // break out of the attribute. escapeHtml only escapes
-                        // <, >, &, not ", so attribute-context interpolation
-                        // would be unsafe.
+                        // break out of the attribute. escapeHtml now escapes
+                        // quotes too, but setting the property directly cannot
+                        // be got wrong at all, so it stays.
                        const iconEl = document.createElement('i');
                        iconEl.className = plugin.icon || 'fas fa-puzzle-piece';
                        const labelNode = document.createTextNode(plugin.name || plugin.id);
@@ -643,10 +643,15 @@
                    }
                },

+                // Quotes too, so the result is safe inside a quoted attribute
+                // value -- the textContent/innerHTML round-trip alone only
+                // escapes &, < and >.
                escapeHtml(text) {
                    const div = document.createElement('div');
                    div.textContent = text;
-                    return div.innerHTML;
+                    return div.innerHTML
+                        .replace(/"/g, '&quot;')
+                        .replace(/'/g, '&#39;');
                },

                async refreshPlugins() {
@@ -260,6 +260,9 @@ function closeErrorModal() {

 /**
 * Escape HTML to prevent XSS.
+ *
+ * Quotes are escaped as well so the result is safe inside a quoted attribute
+ * value -- the textContent/innerHTML round-trip alone only escapes &, < and >.
 */
 function escapeHtml(text) {
    if (typeof text !== 'string') {
@@ -267,7 +270,9 @@ function escapeHtml(text) {
    }
    const div = document.createElement('div');
    div.textContent = text;
-    return div.innerHTML;
+    return div.innerHTML
+        .replace(/"/g, '&quot;')
+        .replace(/'/g, '&#39;');
 }

 /**
@@ -118,15 +118,27 @@
        /**
         * Escape HTML to prevent XSS
         * Always escapes the input, even for non-strings, by coercing to string first
+         *
+         * The result is safe in text content AND inside quoted attribute values.
+         * The textContent/innerHTML round-trip only escapes `&`, `<` and `>` --
+         * the HTML serializer leaves quotes alone because they are harmless in a
+         * text node. Every widget here interpolates the result into attributes
+         * (`value="${escapeHtml(v)}"`), where an unescaped `"` closes the
+         * attribute and lets the value inject its own, so the quotes have to go
+         * too. Each widget's standalone fallback already did this; the shared
+         * implementation they all prefer did not.
+         *
         * @param {*} text - Text to escape (will be coerced to string)
-         * @returns {string} Escaped text
+         * @returns {string} Escaped text, safe for text and attribute contexts
         */
        escapeHtml(text) {
            // Always coerce to string first, then escape
            const textStr = String(text);
            const div = document.createElement('div');
            div.textContent = textStr;
-            return div.innerHTML;
+            return div.innerHTML
+                .replace(/"/g, '&quot;')
+                .replace(/'/g, '&#39;');
        }
        
        /**
@@ -50,10 +50,14 @@
            }
            
            // Escape HTML to prevent XSS (for HTML contexts)
+            // Quotes too: the result lands in quoted attribute values below, and
+            // the textContent/innerHTML round-trip only escapes &, < and >.
            const escapeHtml = (text) => {
                const div = document.createElement('div');
-                div.textContent = text;
-                return div.innerHTML;
+                div.textContent = String(text ?? '');
+                return div.innerHTML
+                    .replace(/"/g, '&quot;')
+                    .replace(/'/g, '&#39;');
            };
            
            // Use validated/sanitized hex for style attribute and input values
@@ -804,10 +804,14 @@
        const schedule = image.schedule || { enabled: false, mode: 'always', start_time: '08:00', end_time: '18:00', days: {} };
        
        // Escape HTML helper
+        // Quotes too: the result lands in quoted attribute values below, and the
+        // textContent/innerHTML round-trip only escapes &, < and >.
        const escapeHtml = (text) => {
            const div = document.createElement('div');
-            div.textContent = text;
-            return div.innerHTML;
+            div.textContent = String(text ?? '');
+            return div.innerHTML
+                .replace(/"/g, '&quot;')
+                .replace(/'/g, '&#39;');
        };
        
        // Use sanitizedId for all ID references in the schedule HTML
@@ -738,10 +738,15 @@
            delete btn._jfmOrigText;
        }

+        // Quotes too: the result lands in quoted attribute values (title=,
+        // data-cat=, pattern=, ...), and the textContent/innerHTML round-trip
+        // only escapes &, < and >.
        _esc(str) {
            const d = document.createElement('div');
            d.textContent = String(str ?? '');
-            return d.innerHTML;
+            return d.innerHTML
+                .replace(/"/g, '&quot;')
+                .replace(/'/g, '&#39;');
        }

        _fmtSize(bytes) {
@@ -206,10 +206,15 @@
        else console.log(`[PFM][${type}] ${msg}`);
    }

+    // Quotes too: the result lands in quoted attribute values (id=, value=,
+    // data-col=), and the textContent/innerHTML round-trip only escapes
+    // &, < and >.
    function escHtml(s) {
        const d = document.createElement('div');
        d.textContent = String(s ?? '');
-        return d.innerHTML;
+        return d.innerHTML
+            .replace(/"/g, '&quot;')
+            .replace(/'/g, '&#39;');
    }

    function formatSize(bytes) {
@@ -383,7 +388,7 @@
                <button class="pfm-btn pfm-btn-primary" id="${escHtml(fieldId)}_save_btn">
                    <i class="fas fa-save mr-1"></i>Save
                </button>
-            </div>`;
+            </div>`);
        overlay.appendChild(modal);
        // Bind events after DOM insertion — filename captured in closure, not in HTML.
        modal.querySelector(`#${CSS.escape(fieldId)}_modal_close`).addEventListener('click', () => window._pfmCloseModal(fieldId));
@@ -411,7 +416,7 @@
                <textarea id="${escHtml(fieldId)}_json_ta" rows="20"
                    style="width:100%;font-family:monospace;font-size:.75rem;border:1px solid #d1d5db;border-radius:.375rem;padding:.5rem;"
                >${escHtml(JSON.stringify(content, null, 2))}</textarea>
-                <div id="${escHtml(fieldId)}_json_err" style="color:#dc2626;font-size:.75rem;margin-top:.25rem;"></div>`;
+                <div id="${escHtml(fieldId)}_json_err" style="color:#dc2626;font-size:.75rem;margin-top:.25rem;"></div>`);
        }
    };

@@ -431,6 +436,20 @@
        if (!entries.length) { container.textContent = 'No entries.'; return; }

        const cols = Object.keys(entries[0][1]);
+
+        // Delegated listener: day/col reach _pfmCellEdit only through data-*
+        // attributes, never through a JS string spliced into an inline
+        // handler -- the browser HTML-decodes attribute values before
+        // running them as script, which undoes escHtml's quote escaping and
+        // reopens the exact injection it exists to close. `container` is a
+        // fresh element per modal open (see _pfmOpenEdit), so this attaches
+        // exactly once per table, even though buildPage() re-renders below.
+        container.addEventListener('input', (e) => {
+            const cell = e.target.closest('input[data-day], textarea[data-day]');
+            if (!cell) return;
+            window._pfmCellEdit(fieldId, cell.dataset.day, cell.dataset.col, cell.value);
+        });
+
        const MS_PER_DAY = 86400 * 1000; // eslint-disable-line no-magic-numbers -- 86400s/day is not magic
        const todayDoy = Math.ceil((new Date() - new Date(new Date().getFullYear(), 0, 0)) / MS_PER_DAY);
        const total = entries.length;
@@ -459,18 +478,16 @@
                        </thead>
                        <tbody>
                            ${pageEntries.map(([day, val]) => `
-                            <tr data-day="${day}" class="${parseInt(day) === todayDoy ? 'today-row' : ''}">
+                            <tr data-day="${escHtml(day)}" class="${parseInt(day) === todayDoy ? 'today-row' : ''}">
                                <td class="pfm-day-col" style="user-select:none;">${escHtml(day)}</td>
                                ${cols.map(col => {
                                    const v = val[col] ?? '';
                                    const isLong = String(v).length > 60 || col === 'description' || col === 'definition' || col === 'content';
                                    return isLong
-                                        ? `<td><textarea data-day="${day}" data-col="${escHtml(col)}" rows="2"
-                                            oninput="window._pfmCellEdit('${fieldId}','${day}','${escHtml(col)}',this.value)"
+                                        ? `<td><textarea data-day="${escHtml(day)}" data-col="${escHtml(col)}" rows="2"
                                            >${escHtml(String(v))}</textarea></td>`
-                                        : `<td><input type="text" data-day="${day}" data-col="${escHtml(col)}"
-                                            value="${escHtml(String(v))}"
-                                            oninput="window._pfmCellEdit('${fieldId}','${day}','${escHtml(col)}',this.value)"></td>`;
+                                        : `<td><input type="text" data-day="${escHtml(day)}" data-col="${escHtml(col)}"
+                                            value="${escHtml(String(v))}"></td>`;
                                }).join('')}
                            </tr>`).join('')}
                        </tbody>
@@ -489,7 +506,7 @@
                                ${page >= totalPages ? 'disabled' : ''}
                                onclick="window._pfmTablePage('${fieldId}',${page + 1})">Next ›</button>
                    </div>
-                </div>`;
+                </div>`);
            st._tablePage = page;
            st._tableEntries = entries;
            st._tableCols = cols;
@@ -578,7 +595,7 @@
                <button class="pfm-btn pfm-btn-danger" id="${escHtml(fieldId)}_del_confirm">
                    <i class="fas fa-trash mr-1"></i>Delete
                </button>
-            </div>`;
+            </div>`);
        overlay.appendChild(modal);
        modal.querySelector(`#${CSS.escape(fieldId)}_del_close`).addEventListener('click', () => window._pfmCloseModal(fieldId));
        modal.querySelector(`#${CSS.escape(fieldId)}_del_cancel`).addEventListener('click', () => window._pfmCloseModal(fieldId));
@@ -631,7 +648,7 @@
                    <i class="fas fa-plus mr-1"></i>Create
                </button>
            </div>
-            </div>`;
+            </div>`);
        overlay.appendChild(modal);
        modal.querySelector(`#${CSS.escape(fieldId)}_cre_close`).addEventListener('click', () => window._pfmCloseModal(fieldId));
        modal.querySelector(`#${CSS.escape(fieldId)}_cre_cancel`).addEventListener('click', () => window._pfmCloseModal(fieldId));
@@ -784,7 +801,7 @@
                    <div class="pfm-grid">
                        <div class="pfm-empty"><i class="fas fa-spinner fa-spin"></i>Loading…</div>
                    </div>
-                </div>`;
+                </div>`);

            loadFiles(fieldId);
        },
@@ -54,9 +54,16 @@
    // RFC 3986 scheme pattern: starts with letter, then letters/digits/+/./-
    const RFC_SCHEME_PATTERN = /^[A-Za-z][A-Za-z0-9+.-]*$/;

+    // Schemes that execute script when navigated to. These can never be
+    // allowed, whatever a schema's allowedProtocols asks for: the validated
+    // value is written straight into an <a href>, so allowing "javascript"
+    // here would turn a config field into script execution.
+    const SCRIPTABLE_SCHEMES = ['javascript', 'data', 'vbscript', 'blob', 'filesystem'];
+
    /**
     * Normalize and validate protocol list against RFC 3986 scheme pattern.
     * Accepts schemes like "http", "https", "git+ssh", "android-app", etc.
+     * Scriptable schemes are dropped -- see SCRIPTABLE_SCHEMES.
     * @param {Array|string} protocols - Protocol list (array or comma-separated string)
     * @returns {Array} Normalized lowercase protocols, defaults to ['http', 'https']
     */
@@ -70,15 +77,25 @@
        const normalized = list
            .map(p => String(p).trim())
            .filter(p => RFC_SCHEME_PATTERN.test(p))
-            .map(p => p.toLowerCase());
+            .map(p => p.toLowerCase())
+            .filter(p => !SCRIPTABLE_SCHEMES.includes(p));
        return normalized.length > 0 ? normalized : ['http', 'https'];
    }

+    /**
+     * True when `string` parses as a URL whose scheme is allowed AND is not
+     * one that executes script. The scriptable check is repeated here rather
+     * than trusted to normalizeProtocols so that a caller passing its own
+     * protocol list cannot re-open the hole.
+     */
    function isValidUrl(string, allowedProtocols) {
        try {
            const url = new URL(string);
+            const protocol = url.protocol.replace(':', '').toLowerCase();
+            if (SCRIPTABLE_SCHEMES.includes(protocol)) {
+                return false;
+            }
            if (allowedProtocols && allowedProtocols.length > 0) {
-                const protocol = url.protocol.replace(':', '').toLowerCase();
                return allowedProtocols.includes(protocol);
            }
            return true;
@@ -87,6 +104,15 @@
        }
    }

+    /**
+     * A value safe to use as an <a href>: the URL itself when it validates,
+     * and '' otherwise. Keeps the "render an href for whatever is stored"
+     * path from emitting a javascript: URL that was never validated.
+     */
+    function safeHref(value, allowedProtocols) {
+        return isValidUrl(value, allowedProtocols) ? value : '';
+    }
+
    window.LEDMatrixWidgets.register('url-input', {
        name: 'URL Input Widget',
        version: '1.0.0',
@@ -139,7 +165,7 @@
                html += `
                    <div id="${fieldId}_preview" class="mt-2 ${currentValue && isValidUrl(currentValue, allowedProtocols) ? '' : 'hidden'}">
                        <a id="${fieldId}_preview_link"
-                           href="${escapeHtml(currentValue)}"
+                           href="${escapeHtml(safeHref(currentValue, allowedProtocols))}"
                           target="_blank"
                           rel="noopener noreferrer"
                           class="text-sm text-blue-600 hover:text-blue-800 flex items-center">
@@ -231,10 +257,23 @@
                const protocols = normalizeProtocols(widgetEl?.dataset.protocols);

                if (previewEl && previewLink) {
-                    if (value && isValidUrl(value, protocols)) {
+                    // Scheme checked inline, right where the value reaches the DOM sink,
+                    // rather than through safeHref/isValidUrl -- CodeQL's DOM-based-XSS
+                    // sanitizer recognition does not trace a boolean-returning helper two
+                    // calls deep, so it kept flagging this assignment even though the
+                    // scriptable-scheme check (see SCRIPTABLE_SCHEMES) already covered it.
+                    let scheme = '';
+                    try {
+                        scheme = value ? new URL(value).protocol.replace(':', '').toLowerCase() : '';
+                    } catch (_) {
+                        scheme = '';
+                    }
+                    const schemeIsSafe = !!scheme && !SCRIPTABLE_SCHEMES.includes(scheme) && protocols.includes(scheme);
+                    if (schemeIsSafe) {
                        previewLink.href = value;
                        previewEl.classList.remove('hidden');
                    } else {
+                        previewLink.removeAttribute('href');
                        previewEl.classList.add('hidden');
                    }
                }
@@ -4370,12 +4370,15 @@ function renderCustomRegistryPlugins(plugins, registryUrl) {
        return;
    }

-    // Escape HTML helper
+    // Escape HTML helper. Quotes too: the result lands in quoted attribute
+    // values, and the textContent/innerHTML round-trip only escapes &, < and >.
    const escapeHtml = (text) => {
        if (!text) return '';
        const div = document.createElement('div');
        div.textContent = text;
-        return div.innerHTML;
+        return div.innerHTML
+            .replace(/"/g, '&quot;')
+            .replace(/'/g, '&#39;');
    };

    // Helper function to escape for JavaScript strings
@@ -4471,11 +4474,15 @@ function isGithubUrl(url) {
    }
 }

-// Utility function to escape HTML
+// Utility function to escape HTML. Quotes too: most call sites interpolate the
+// result into a quoted attribute value, and the textContent/innerHTML
+// round-trip only escapes &, < and >.
 function escapeHtml(text) {
    const div = document.createElement('div');
    div.textContent = text;
-    return div.innerHTML;
+    return div.innerHTML
+        .replace(/"/g, '&quot;')
+        .replace(/'/g, '&#39;');
 }

 // Utility function to escape text for use in HTML attributes
@@ -5623,11 +5630,15 @@ document.addEventListener('htmx:afterSettle', function() {
    let starlarkDataLoaded = false;

    // ── Helpers ─────────────────────────────────────────────────────────────
+    // Quotes too: the result lands in quoted attribute values (data-app-id=,
+    // title=), and the textContent/innerHTML round-trip only escapes &, < and >.
    function escapeHtml(str) {
        if (!str) return '';
        const div = document.createElement('div');
        div.textContent = str;
-        return div.innerHTML;
+        return div.innerHTML
+            .replace(/"/g, '&quot;')
+            .replace(/'/g, '&#39;');
    }

    function isStarlarkInstalled(appId) {
@@ -152,7 +152,8 @@ function displayCacheFiles(data) {
                <span class="text-sm text-gray-600">${escapeHtml(modifiedStr)}</span>
            </td>
            <td class="px-6 py-4 whitespace-nowrap text-right text-sm font-medium">
-                <button onclick="deleteCacheFile('${escapeHtml(cacheFile.key)}')" 
+                <button onclick="deleteCacheFile(this.dataset.cacheKey)"
+                        data-cache-key="${escapeHtml(cacheFile.key)}"
                        class="text-red-600 hover:text-red-900 px-3 py-1 rounded hover:bg-red-50 transition-colors"
                        title="Delete cache file">
                    <i class="fas fa-trash mr-1"></i>Delete
@@ -220,10 +221,14 @@ function showError(message) {
 }

 // Utility function to escape HTML
+// Quotes too: the result is interpolated into quoted attribute values, and the
+// textContent/innerHTML round-trip only escapes &, < and >.
 function escapeHtml(text) {
    const div = document.createElement('div');
    div.textContent = text;
-    return div.innerHTML;
+    return div.innerHTML
+        .replace(/"/g, '&quot;')
+        .replace(/'/g, '&#39;');
 }

 // Make deleteCacheFile available globally for onclick handlers
@@ -711,11 +711,15 @@ function showError(message) {
    }
 }

-// Utility function to escape HTML
+// Utility function to escape HTML. Quotes too: the result is interpolated into
+// quoted attribute values (option value=, title=), and the
+// textContent/innerHTML round-trip only escapes &, < and >.
 function escapeHtml(text) {
    const div = document.createElement('div');
    div.textContent = text;
-    return div.innerHTML;
+    return div.innerHTML
+        .replace(/"/g, '&quot;')
+        .replace(/'/g, '&#39;');
 }

 function refreshCurrentPluginStatus() {