Trix is vulnerable to XSS through JSON deserialization bypass in drag-and-drop (Level0InputController)
Date: 2026-03
Affected: rubygems/action_text-trix, npm/trix
Attack vector: xss
Category: vulnerability-disclosure
Severity: Low
CWE: CWE-79

### Impact The Trix editor, in versions prior to 2.1.18, is vulnerable to XSS when a crafted `application/x-trix-document` JSON payload is dropped into the editor in environments using the fallback Level0InputController (e.g., embedded WebViews lacking Input Events Level 2 support). The `StringPiece.fromJSON` method trusted `href` attributes from the JSON payload without sanitization. An attacker could craft a draggable element containing a `javascript:` URI in the href attribute that, when dropped into a vulnerable editor, would bypass DOMPurify sanitization and inject executable JavaScript into the DOM. Exploitation requires a specific environment (Level0InputController fallback) and social engineering (victim must drag and drop attacker-controlled content into the editor). Applications using server-side HTML sanitization (such as Rails' built-in sanitizer) are additionally protected, as the payload is neutralized on save. ### Patches Update Recommendation: Users should upgrade to Trix editor version 2.1.18 or later. ### References The XSS vulnerability was responsibly reported by Hackerone researcher [newbiefromcoma](https://hackerone.com/newbiefromcoma).


Mitigations:

Architectural layers (MAESTRO):