{"id":"GHSA-53g2-mvcc-q9x3","summary":"Trix: Stored XSS via HTMLParser attribute injection on paste","details":"### Impact\n\nThe Trix editor, in versions prior to 2.1.18, is vulnerable to XSS when crafted HTML is pasted into the editor. The `HTMLParser` processed a mock attachment, a `\u003cspan\u003e` carrying an empty `data-trix-attachment=\"{}\"`. The empty attachment object caused the element to bypass attachment handling, so its `data-trix-attributes` were applied to a plain string piece. The pre-2.1.18 `StringPiece.fromJSON` accepted the `href` without validation, so an attacker-supplied `javascript:` URI was carried into the document model and emitted verbatim into the serialized HTML, executing when the content was rendered and clicked.\n\nThis is a stored XSS in any application that accepts untrusted rich text through Trix and renders the serialized output to other users. Applications that apply server-side HTML sanitization, such as the Rails built-in sanitizer, are additionally protected because the payload is neutralized on save.\n\nThis vulnerability shares its fix with GHSA-53p3-c7vp-4mcc. Both are resolved by the `StringPiece.fromJSON` sanitization added in 2.1.18. This advisory covers the paste and HTMLParser entry vector, while GHSA-53p3-c7vp-4mcc covers the drag-and-drop path through the fallback Level0InputController.\n\n### Patches\n\nUsers should upgrade to Trix editor version 2.1.18 or later.\n\n### References\n\nThe vulnerability was responsibly reported by HackerOne researcher [newbiefromcoma](https://hackerone.com/newbiefromcoma).","aliases":["CVE-2026-73428"],"modified":"2026-08-12T21:11:05.764982Z","published":"2026-07-24T16:18:01Z","database_specific":{"github_reviewed_at":"2026-07-24T16:18:01Z","nvd_published_at":null,"cwe_ids":["CWE-79"],"severity":"MODERATE","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/basecamp/trix/security/advisories/GHSA-53g2-mvcc-q9x3"},{"type":"WEB","url":"https://github.com/basecamp/trix/commit/9c0a993d9fc2ffe9d56b013b030bc238f9c0557c"},{"type":"PACKAGE","url":"https://github.com/basecamp/trix"},{"type":"WEB","url":"https://github.com/basecamp/trix/releases/tag/v2.1.18"}],"affected":[{"package":{"name":"trix","ecosystem":"npm","purl":"pkg:npm/trix"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.1.18"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-53g2-mvcc-q9x3/GHSA-53g2-mvcc-q9x3.json"}},{"package":{"name":"action_text-trix","ecosystem":"RubyGems","purl":"pkg:gem/action_text-trix"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.1.18"}]}],"versions":["0.0.1","2.1.15","2.1.16","2.1.17"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-53g2-mvcc-q9x3/GHSA-53g2-mvcc-q9x3.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N"}]}