Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
In MODX Revolution before 2.5.7, when PHP 5.3.3 is used, an attacker is able to include and execute arbitrary files on the web server due to insufficient validation of the action parameter to setup/index.php, aka directory traversal.
CWE-22 - Path Traversal
Path traversal (or directory traversal), is a vulnerability that allows malicious users to traverse the server's root directory, gaining access to arbitrary files and folders such as application code & data, back-end credentials, and sensitive operating system files. In the worst-case scenario, an attacker could potentially execute arbitrary files on the server, resulting in a denial of service attack. Such an exploit may severely impact the integrity, confidentiality, and availability of an application.