Exponent CMS 2.4 uses PHP reflection to call a method of a controller class, and then uses the method name to check user permission.

Summary

Exponent CMS 2.4 uses PHP reflection to call a method of a controller class, and then uses the method name to check user permission. But, the method name in PHP reflection is case insensitive, and Exponent CMS permits undefined actions to execute by default, so an attacker can use a capitalized method name to bypass the permission check, e.g., controller=expHTMLEditor&action=preview&editor=ckeditor and controller=expHTMLEditor&action=Preview&editor=ckeditor. An anonymous user will be rejected for the former but can access the latter.