Basecamp Trix up to 2.1.17 HTMLParser/StringPiece StringPiece.fromJSON HTML injection

Summaryinfo

A vulnerability was found in Basecamp Trix up to 2.1.17 and classified as problematic. The impacted element is the function StringPiece.fromJSON of the component HTMLParser/StringPiece. The manipulation results in HTML injection. This vulnerability is identified as CVE-2026-73428. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Basecamp Trix up to 2.1.17. Affected is the function StringPiece.fromJSON of the component HTMLParser/StringPiece. The manipulation with an unknown input leads to a html injection vulnerability. CWE is classifying the issue as CWE-79. 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. This is going to have an impact on integrity. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-73428 since 08/12/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project.

Upgrading to version 2.1.18 eliminates this vulnerability.

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Productinfo

Vendor

• Basecamp

Name

• Trix

Version

• 2.1.0
• 2.1.1
• 2.1.2
• 2.1.3
• 2.1.4
• 2.1.5
• 2.1.6
• 2.1.7
• 2.1.8
• 2.1.9
• 2.1.10
• 2.1.11
• 2.1.12
• 2.1.13
• 2.1.14
• 2.1.15
• 2.1.16
• 2.1.17

Website

• Product: https://github.com/basecamp/trix/

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