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Vulnerability · Published Jul 1, 2026 · Assigned by GitHub_M

CVE-2026-55660TinaCMS: Cross-origin postMessage handlers and rich-text URL-sanitization bypass enable stored XSS and session takeover

High 7.6

In plain English

A high-severity cross-site scripting in tinacms from tinacms. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)7.6High
Exploit odds (30 days)0.3%top 79.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
npm@tinacms/app2.5.6GHSA-g5qx-h5f3-mp2f
npmtinacms3.9.3GHSA-g5qx-h5f3-mp2f

Affected products (as reported)

VendorProductVersions
tinacms tinacms < 3.9.3
tinacms @tinacms/app < 2.5.6

Weakness: CWE-79, CWE-346, CWE-601, CWE-940 · Vector: 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

References