{"id":"CVE-2026-55660","aliases":["GHSA-g5qx-h5f3-mp2f"],"url":"https://o3.security/vulnerability/CVE-2026-55660","summary":"TinaCMS: Cross-origin postMessage handlers and rich-text URL-sanitization bypass enable stored XSS and session takeover","details":"Tina is a headless content management system. In versions prior to @tinacms/app 2.5.6 and tinacms 3.9.3, cross-origin postMessage handlers and a rich-text URL-sanitization bypass enable stored XSS and session takeover. The library registers window message listeners — the useTina overlay handler, the OAuth authentication popup handler, and the admin↔preview iframe GraphQL reducer — that act on event.data without verifying event.origin or event.source and post messages using non-specific target origins, while insufficient URL sanitization in rich-text content allows malicious URLs to persist and execute. A page the victim visits (or a window in an opener/iframe relationship with a Tina admin) can forge messages to drive the editor, inject preview content, or observe/forge the OAuth popup channel to take over an authenticated editing session. This issue has been fixed in versions @tinacms/app 2.5.6 and tinacms 3.9.3.","published":"2026-07-01T21:00:27.321Z","modified":"2026-08-12T03:51:30.127116958Z","cvss":null,"epss":{"score":0.00196,"percentile":0.09652,"asOf":"2026-08-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"tinacms","fixedVersion":"3.9.3"},{"ecosystem":"npm","name":"@tinacms/app","fixedVersion":"2.5.6"}],"fix":{"url":"https://github.com/tinacms/tinacms/pull/7056","label":"tinacms/tinacms#7056"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55660.json"},{"type":"ADVISORY","url":"https://github.com/tinacms/tinacms/security/advisories/GHSA-g5qx-h5f3-mp2f"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55660"},{"type":"FIX","url":"https://github.com/tinacms/tinacms/pull/7056"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:30.127116958Z"}}