source: https://www.securityfocus.com/bid/13996/info

It is reported that cPanel is prone to a cross-site scripting vulnerability that may allow a remote attacker to execute HTML or script code in a user's browser. The issue presents itself due to insufficient sanitization of user-supplied data via the 'user' parameter of the 'login' page.

Due to the possibility of attacker-specified HTML and script code being rendered in a victim's browser, it is possible to steal cookie-based authentication credentials from that user. Other attacks are possible as well. 

http://www.example.com:2082/login?user=**<script>JavaScript:alert(document.cookie);</script>