source: http://www.securityfocus.com/bid/24748/info

Moodle is prone to a cross-site scripting vulnerability because it fails to properly sanitize user-supplied input.

Exploiting this vulnerability may allow an attacker to perform cross-site scripting attacks on unsuspecting users in the context of the affected website. As a result, the attacker may be able to steal cookie-based authentication credentials and to launch other attacks.

This issue affects Moodle 1.7.1; other versions may also be vulnerable. 

http://www.example.com/user/index.php?contextid=4&roleid=0&id=2&group=&perpage=20&search=%22style=xss:expression(alert(document.cookie))%20 