CVE-2026-27591: Winter vulnerable to privilege escalation by authenticated backend users

Affected versions of Winter CMS allowed authenticated backend users to escalate their accounts level of access to the system by modifying the roles / permissions assigned to their account through specially crafted requests to the backend while logged in.

To actively exploit this security issue, an attacker would need access to the Backend with a user account with any level of access.

The Winter CMS maintainers strongly recommend that all Winter CMS sites that have any reliance on the roles & permissions system to update immediately. Security fixes have been backported to all major versions of Winter (1.0, 1.1, and 1.2).