Trix is a what-you-see-is-what-you-get rich text editor for everyday writing. Prior to 2.1.18, Trix is vulnerable to cross-site scripting when a crafted application/x-trix-document JSON payload is dropped into an editor using the fallback Level0InputController, such as an embedded WebView without Input Events Level 2 support. The StringPiece.fromJSON method trusts href attributes from the JSON payload without sanitization, allowing a draggable element containing a javascript: URI to bypass DOMPurify sanitization and inject executable JavaScript into the DOM. Exploitation requires the victim to drag and drop attacker-controlled content, and server-side HTML sanitization can neutralize the payload on save. This issue is fixed in version 2.1.18.

Affected: npm: trix, RubyGems: action_text-trix

### 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).