Craft CMS is a content management system (CMS). In versions 5.9.0 and above prior to 5.10.0, control panel users with the ability to edit entries can execute unsandboxed Twig code via the HTTP Referrer header, potentially leading to authenticated RCE. The issue happens when a user is saving entries. Strings for a signed redirect URL are being compiled as a Twig template via renderObjectTemplate(), and while a sandboxed alternative already exists (renderSandboxedObjectTemplate()), it is not used in this case. This signed URL can be specified by users, as it is reflected in the “Referer” HTTP request header, which is under attacker control. This issue has been fixed in version 5.10.0.

Craft CMS: Potential authenticated Remote Code Execution via referrer redirect