{"id":"GHSA-9fww-8cpr-q66r","summary":"Isso affected by Stored XSS via comment website field","details":"## Impact\n\nThis is a stored Cross-Site Scripting (XSS) vulnerability affecting the website and author comment fields. The website field was HTML-escaped using quote=False, which left single and double quotes unescaped. Since the frontend inserts the website value directly into a single-quoted href attribute via string concatenation, a single quote in the URL breaks out of the attribute context, allowing injection of arbitrary event handlers (e.g. onmouseover, onclick).\n\nThe same escaping was missing entirely from the user-facing comment edit endpoint (PUT /id/\u003cid\u003e) and the moderation edit endpoint (POST /id/\u003cid\u003e/edit/\u003ckey\u003e).\n\nAny visitor to a page embedding isso comments is impacted. No authentication or interaction beyond mouse movement is required to trigger a payload — an attacker can post a comment anonymously (moderation is off by default) with a crafted website URL, and the payload persists in the database and fires on every page load. With the full-page invisible overlay technique described in the report, the victim only needs to move their mouse.\n\n## Patches\n\nThe issue is fixed in commit 3cf27c2. Users should upgrade to a version containing that commit once released. The fix applies html.escape(..., quote=True) to the website field across all three write paths (POST /new, PUT /id/\u003cid\u003e, POST /id/\u003cid\u003e/edit/\u003ckey\u003e), and adds input validation and escaping to the moderation edit endpoint which previously had neither.\n\n## Workarounds\n\n  Enabling comment moderation (moderation = enabled = true in isso.cfg) prevents unauthenticated users from publishing comments, raising the bar for exploitation. However, it\n  does not fully mitigate the issue since a moderator activating a malicious comment would still expose visitors. There is no configuration-only workaround that fully prevents\n   the vulnerability.\n\n## Resources\n\n  - https://docs.python.org/3/library/html.html#html.escape — note the quote parameter","aliases":["CVE-2026-27469","PYSEC-2026-2527"],"modified":"2026-07-13T16:42:33.405962889Z","published":"2026-02-24T16:03:04Z","database_specific":{"github_reviewed_at":"2026-02-24T16:03:04Z","nvd_published_at":"2026-02-21T08:16:11Z","cwe_ids":["CWE-116","CWE-79"],"severity":"MODERATE","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/isso-comments/isso/security/advisories/GHSA-9fww-8cpr-q66r"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27469"},{"type":"WEB","url":"https://github.com/isso-comments/isso/commit/0afbfe0691ee237963e8fb0b2ee01c9e55ca2144"},{"type":"WEB","url":"https://docs.python.org/3/library/html.html#html.escape"},{"type":"PACKAGE","url":"https://github.com/isso-comments/isso"}],"affected":[{"package":{"name":"isso","ecosystem":"PyPI","purl":"pkg:pypi/isso"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.13.2"}]}],"versions":["0.10","0.10.1","0.10.2","0.10.3","0.10.4","0.10.5","0.10.6","0.11.0","0.11.1","0.12.0","0.12.1","0.12.2","0.12.4","0.12.5","0.12.6","0.12.6.1","0.12.6.2","0.13.0","0.13.1.dev0","0.8","0.8.1","0.8.2","0.8.3","0.9","0.9.1","0.9.10","0.9.2","0.9.3","0.9.4","0.9.5","0.9.6","0.9.7","0.9.8","0.9.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-9fww-8cpr-q66r/GHSA-9fww-8cpr-q66r.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"}]}