GHSA-fp5j-j7j4-mcxc CraftCMS has an RCE vulnerability via relational conditionals in the control panel

• Packagist craftcms/cms: >= 5.0.0-RC1, < 5.9.9 → fixed in 5.9.9 • Packagist craftcms/cms: >= 4.0.0-beta.1, < 4.17.4 → fixed in 4.17.4

A Remote Code Execution vulnerability exists in the Craft CMS 5 conditions system. The `BaseElementSelectConditionRule::getElementIds()` method passes user-controlled string input through `renderObjectTemplate()` -- an unsandboxed Twig rendering function with escaping disabled. Any authenticated Control Panel user (including non-admin roles such as Author or Editor) can achieve full RCE by sending a crafted condition rule via standard element listing endpoints. This vulnerability requires no admin privileges, no special permissions beyond basic control panel access, and bypasses all production hardening settings (allowAdminChanges: false, devMode: false, enableTwigSandbox: true). Users should update to the patched 5.99 release to mitigate the issue.