GetSimple CMS is a content management system. The massiveAdmin plugin (v6.0.3) bundled with GetSimpleCMS-CE v3.3.22 allows an authenticated administrator to overwrite the gsconfig.php configuration file with arbitrary PHP code via the gsconfig editor module. The form lacks CSRF protection, enabling a remote unauthenticated attacker to exploit this via Cross-Site Request Forgery against a logged-in admin, achieving Remote Code Execution (RCE) on the web server.