GHSA-53G2-MVCC-Q9X3
Vulnerability from github – Published: 2026-07-24 16:18 – Updated: 2026-08-12 20:52Impact
The 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.
This 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.
This 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.
Patches
Users should upgrade to Trix editor version 2.1.18 or later.
References
The vulnerability was responsibly reported by HackerOne researcher newbiefromcoma.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "trix"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.18"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "RubyGems",
"name": "action_text-trix"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.18"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-73428"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-24T16:18:01Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"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).",
"id": "GHSA-53g2-mvcc-q9x3",
"modified": "2026-08-12T20:52:01Z",
"published": "2026-07-24T16:18:01Z",
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "Trix: Stored XSS via HTMLParser attribute injection on paste"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.