What’s Vulnerable › Vulnerabilities

CVE-2026-73428: Trix: Stored XSS via HTMLParser attribute injection on paste

• Severity: medium (CVSS 4.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-13 · updated 2026-09-18
• Weakness: CWE-79

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.

Affected products

• basecamp trix: before 2.1.18

References

• https://github.com/basecamp/trix/commit/9c0a993d9fc2ffe9d56b013b030bc238f9c0557c
• https://github.com/basecamp/trix/pull/1293
• https://github.com/basecamp/trix/releases/tag/v2.1.18
• https://github.com/basecamp/trix/security/advisories/GHSA-53g2-mvcc-q9x3

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