Trix: Stored XSS via HTMLParser attribute injection on paste

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.6 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

EPSS

• CVE-2026-73428: 0.35% estimated exploitation activity in the next 30 days; percentile 29.05 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The Trix editor, in versions prior to 2.1.18, is vulnerable to XSS when crafted HTML is pasted into the editor. The HTMLParser processed a mock attachment, a <span carrying an empty data-trix-attachment="{}". The empty attachment object caused the element to bypass attachment handling, so its data-trix-attributes were applied to a plain string piece. The pre-2.1.18 StringPiece.fromJSON accepted the href without validation, so an attacker-supplied javascript: URI was carried into the document model and emitted verbatim into the serialized HTML, executing when the content was rendered and clicked. This is a stored XSS in any application that accepts untrusted rich text through Trix and renders the serialized output to other users. Applications that apply server-side HTML sanitization, such as the Rails built-in sanitizer, are additionally protected because the payload is neutralized on save. This vulnerability shares its fix with GHSA-53p3-c7vp-4mcc. Both are resolved by the…

Published by the source

24 Jul 2026, 16:18 UTC

Last modified by the source

12 Aug 2026, 21:11 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-53g2-mvcc-q9x3

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-53g2-mvcc-q9x3

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# Patch Next advisory brief: CVE-2026-73428

Advisory: Trix: Stored XSS via HTMLParser attribute injection on paste
IDs: CVE-2026-73428, GHSA-53g2-mvcc-q9x3
Record: https://patchnext.com/advisories/cve-2026-73428 (revision 2, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: action_text-trix 2.1.18; trix 2.1.18. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems action_text-trix: affected < 2.1.18; fixed in 2.1.18
- npm trix: affected < 2.1.18; fixed in 2.1.18

## Suggested inspection (read-only)
- RubyGems action_text-trix: check the installed version with your package manager.
- `npm ls trix --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on action_text-trix, trix.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-53g2-mvcc-q9x3 (OSV record GHSA-53g2-mvcc-q9x3 lists affected ranges: npm trix >=0 =0 <2.1.18 (fixed))
- Verified: https://github.com/advisories/GHSA-53g2-mvcc-q9x3 (GitHub-reviewed advisory GHSA-53g2-mvcc-q9x3 lists affected ranges: npm trix >=0 =0 <2.1.18)

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