CVE-2026-73428: basecamp trix Cross-site Scripting

Vulnerability summary

CVE-2026-73428 is a medium (CVSS 4.6) Cross-site Scripting vulnerability in basecamp trix. EPSS estimates a 0.35% chance of exploitation in the next 30 days, higher than 27.5% of scored vulnerabilities.

Timeline

1. 13-08-2026
   PublishedVulnerability first disclosed.
2. 14-08-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.