Cross-site scripting (XSS) vulnerability in the phpCAS client library before 1.1.0, as used in Moodle 1.8.x before 1.8.12 and 1.9.x before 1.9.8, allows remote attackers to inject arbitrary web script or HTML via a crafted URL, which is not properly handled in an error message.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.