CVE-2026-55660
HighCVSS 7.6Exploitation Probability (EPSS)
Low risk10th percentile — higher than 10% of all known CVEs
Summary
A vulnerability in the Tina headless CMS allows stored XSS and session takeover via unverified postMessage handlers and insufficient URL sanitization in rich-text content. An attacker can forge messages to hijack an authenticated editing session.
Risk Assessment
Risk includes session takeover of authenticated editors, injection of malicious content, and data theft. The attack can be performed remotely with minimal user interaction.
Recommendation
Immediately update @tinacms/app to version 2.5.6 or later and tinacms to version 3.9.3 or later. After updating, verify OAuth authentication and postMessage handler configurations.
Original NVD description (English source)
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.