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 stored cross-site scripting when crafted HTML is pasted into the editor. HTMLParser processes a mock attachment in a `<span>` with an empty `data-trix-attachment="{}"` value, causing data-trix-attributes to be applied to a plain string piece. StringPiece.fromJSON accepts an unvalidated href, allowing a javascript: URI to enter the document model and serialized HTML and execute when another user renders and clicks the content. Applications that apply server-side HTML sanitization can neutralize the payload on save. This issue is fixed in version 2.1.18.
https://github.com/basecamp/trix/security/advisories/GHSA-53g2-mvcc-q9x3
https://github.com/basecamp/trix/releases/tag/v2.1.18
https://github.com/basecamp/trix/pull/1293
https://github.com/basecamp/trix/commit/9c0a993d9fc2ffe9d56b013b030bc238f9c0557c