source: http://www.securityfocus.com/bid/10884/info

It is reported that Moodle is vulnerable to a cross-site scripting vulnerability. This issue is due to a failure of the application to properly sanitize user-supplied input prior to including it in dynamic web content.

This issue could permit a remote attacker to create a malicious URI link that includes hostile HTML and script code. If this link were followed, the hostile code may be rendered in the web browser of the victim user. This would occur in the security context of the affected web site and would allow for theft of cookie-based authentication credentials or other attacks.

Versions of Moodle prior to 1.3.4 are reported susceptible to this vulnerability.

http://www.example.com/moodle/mod/forum/post.php?reply=%3Cscript%3Ealert(document.cookie);%3C/script%3E