{"id":"CVE-2026-73428","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-73428","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 `<span>` 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).","published":"2026-07-24T16:18:01Z","modified":"2026-08-12T21:00:06.878237619Z","cvss":{"score":4.6,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"trix","fixedVersion":"2.1.18"},{"ecosystem":"RubyGems","name":"action_text-trix","fixedVersion":"2.1.18"}],"fix":{"url":"https://github.com/basecamp/trix/commit/9c0a993d9fc2ffe9d56b013b030bc238f9c0557c","label":"basecamp/trix@9c0a993"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T21:00:06.878237619Z"}}