# CVE-2026-55660

## Summary

- **CVE ID:** CVE-2026-55660
- **Severity:** HIGH
- **CVSS Score:** 7.6 (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N)
- **CWE:** CWE-79, CWE-346, CWE-601, CWE-940
- **Published:** Jul 1, 2026
- **Last Modified:** Jul 2, 2026

## Description

Tina is a headless content management system. In versions prior to @tinacms/app 2.5.6 and tinacms 3.9.3, cross-origin postMessage handlers and a rich-text URL-sanitization bypass enable stored XSS and session takeover. The library registers window message listeners — the useTina overlay handler, the OAuth authentication popup handler, and the admin↔preview iframe GraphQL reducer — that act on event.data without verifying event.origin or event.source and post messages using non-specific target origins, while insufficient URL sanitization in rich-text content allows malicious URLs to persist and execute. A page the victim visits (or a window in an opener/iframe relationship with a Tina admin) can forge messages to drive the editor, inject preview content, or observe/forge the OAuth popup channel to take over an authenticated editing session. This issue has been fixed in versions @tinacms/app 2.5.6 and tinacms 3.9.3.

## Affected Products

- tinacms — tinacms (< 3.9.3)
- tinacms — @tinacms/app (< 2.5.6)

## References

- [CNA](https://github.com/tinacms/tinacms/security/advisories/GHSA-g5qx-h5f3-mp2f)
- [CNA](https://github.com/tinacms/tinacms/pull/7056)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.28%
- **EPSS Percentile:** 20.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._