Cross-site scripting (XSS) vulnerability in the MNET access-control interface in Moodle before 1.8.13 and 1.9.x before 1.9.9 allows remote attackers to inject arbitrary web script or HTML via vectors involving extended characters in a username.
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.