CVE-2026-53609: Apostrophecms Apostrophe

Critical severity, CVSS 9.1. EPSS: 0.4% chance of exploitation in the next 30 days.

ApostropheCMS is an open-source Node.js content management system. In versions up to and including 4.30.0, `apos.util.set()` traverses dot-notation paths without sanitizing `__proto__`, allowing an authenticated editor to write arbitrary values to `Object.prototype` via the `$pullAll` patch operator. A confirmed gadget in `publicApiCheck()` causes this to bypass authorization on all piece-type REST API endpoints for every subsequent unauthenticated request, for the lifetime of the Node.js process. As of time of publication, no known patched versions are available.

Affected products

• Apostrophecms Apostrophe: up to and including 4.30.0

Published 2026-06-12. Last modified 2026-06-17.