CVE-2026-73428: Basecamp Trix

Medium severity, CVSS 4.6. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Basecamp Trix: before 2.1.18 (fixed in 2.1.18)

Published 2026-08-13. Last modified 2026-09-18.