{"cve":"CVE-2026-27469","nvd":{"published":"2026-02-21T08:16:11.993","modified":"2026-06-17T10:27:12.310","status":"Deferred","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","score":6.1},"cwes":["CWE-79","CWE-116"],"references":["https://docs.python.org/3/library/html.html#html.escape","https://github.com/isso-comments/isso/commit/0afbfe0691ee237963e8fb0b2ee01c9e55ca2144","https://github.com/isso-comments/isso/security/advisories/GHSA-9fww-8cpr-q66r"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:24:17.937441719+00:00"},"epss":{"cve":"CVE-2026-27469","score":0.00259,"percentile":0.17641,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-9fww-8cpr-q66r","url":"https://osv.dev/vulnerability/GHSA-9fww-8cpr-q66r","summary":"Isso affected by Stored XSS via comment website field","modified":"2026-07-13T16:42:33.405962889Z","packages":[{"ecosystem":"PyPI","name":"isso","purl":"pkg:pypi/isso","ranges":["<0.13.2"],"fixed":["0.13.2"]}]},{"id":"PYSEC-2026-2527","url":"https://osv.dev/vulnerability/PYSEC-2026-2527","summary":"Isso affected by Stored XSS via comment website field","modified":"2026-07-13T16:31:58.129063476Z","packages":[{"ecosystem":"PyPI","name":"isso","purl":"pkg:pypi/isso","ranges":["<0.13.2"],"fixed":["0.13.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}