{"id":"CVE-2026-5389","aliases":["GHSA-5vp3-3cg6-2rq3"],"url":"https://o3.security/vulnerability/CVE-2026-5389","summary":"justhtml before 1.13.0 XSS via code fence breakout","details":"justhtml versions before 1.13.0 contain a cross-site scripting vulnerability in the to_markdown() function when serializing attacker-controlled pre content. Attackers can place backticks inside sanitized pre elements to break out of fixed-length code fences, allowing raw HTML to execute when the generated Markdown is rendered by CommonMark or GFM-style renderers.","published":"2026-08-23T13:34:09.865Z","modified":"2026-08-28T11:30:19.260762016Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"justhtml","fixedVersion":"1.13.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5389.json"},{"type":"ADVISORY","url":"https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-5vp3-3cg6-2rq3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5389"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/justhtml-before-xss-via-code-fence-breakout"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-28T11:30:19.260762016Z"}}