{"id":"GHSA-53g2-mvcc-q9x3","title":"Trix: Stored XSS via HTMLParser attribute injection on paste","summary":"Trix: Stored XSS via HTMLParser attribute injection on paste","severity":"medium","cvss":4.6,"cwe":["CWE-79"],"vendor":"trix","product":"trix","ecosystem":"npm","affected":["trix < 2.1.18","action_text-trix < 2.1.18"],"patched":["trix 2.1.18","action_text-trix 2.1.18"],"published":"2026-07-24","updated":"2026-07-24","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-53g2-mvcc-q9x3","references":[{"url":"https://github.com/basecamp/trix/security/advisories/GHSA-53g2-mvcc-q9x3"},{"url":"https://github.com/basecamp/trix/commit/9c0a993d9fc2ffe9d56b013b030bc238f9c0557c"},{"url":"https://github.com/basecamp/trix/releases/tag/v2.1.18"},{"url":"https://github.com/advisories/GHSA-53g2-mvcc-q9x3"}],"tags":["ghsa","npm"],"ingestedAt":"2026-07-24T16:33:09.516Z","slug":"GHSA-53g2-mvcc-q9x3","body":"## Overview\n\n### 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).\n\n## Affected packages\n\n- `trix < 2.1.18`\n- `action_text-trix < 2.1.18`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `trix 2.1.18`\n- `action_text-trix 2.1.18`","depth":"sunlit","depthScore":25,"depthScoreParts":{"impact":25.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}