CI4MS is a CodeIgniter 4-based CMS skeleton that delivers a production-ready, modular architecture with RBAC authorization and theme support. Prior to 0.31.4.0, the Install::index() controller reads the host POST parameter without any validation and passes it directly into updateEnvSettings(), which writes it into the .env file via preg_replace(). Because newline characters in the value are not stripped, an attacker can inject arbitrary configuration directives into the .env file.

The install routes have CSRF protection explicitly disabled, and the InstallFilter can be bypassed when cache('settings') is empty (cache expiry or fresh deployment). This vulnerability is fixed in 0.31.4.0.