{"id":"CVE-2026-27469","aliases":["GHSA-9fww-8cpr-q66r","PYSEC-2026-2527"],"url":"https://o3.security/vulnerability/CVE-2026-27469","summary":"Isso: Stored XSS via comment website field","details":"Isso is a lightweight commenting server written in Python and JavaScript. In commits before 0afbfe0691ee237963e8fb0b2ee01c9e55ca2144, there 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). The same escaping is missing entirely from the user-facing comment edit endpoint (PUT /id/) and the moderation edit endpoint (POST /id//edit/). This issue has been patched in commit 0afbfe0691ee237963e8fb0b2ee01c9e55ca2144. To workaround, nabling comment moderation (moderation = enabled = true in isso.cfg) prevents unauthenticated users from publishing comments, raising the bar for exploitation, but it does not fully mitigate the issue since a moderator activating a malicious comment would still expose visitors.","published":"2026-02-21T07:24:38.971Z","modified":"2026-08-12T03:51:43.462777223Z","cvss":{"score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"isso","fixedVersion":"0.13.2"}],"fix":{"url":"https://github.com/isso-comments/isso/commit/0afbfe0691ee237963e8fb0b2ee01c9e55ca2144","label":"isso-comments/isso@0afbfe0"},"references":[{"type":"WEB","url":"https://docs.python.org/3/library/html.html#html.escape"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27469.json"},{"type":"ADVISORY","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":"FIX","url":"https://github.com/isso-comments/isso/commit/0afbfe0691ee237963e8fb0b2ee01c9e55ca2144"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:43.462777223Z"}}