Original advisory: http://www.davidsopas.com/2009/05/25/arcade-trade-script-xss/

Arcade Trade Script is a full arcade site CMS (Content Management
System) with easy customization and advanced traffic trading system
built in. With ATS you will hardly ever have to FTP anything. Almost
all files, pages, and meta tags can be edited from the admin panel.
ATS is extremely easy to use and works for both regular arcades and
full blown traffic trading arcades. - taken from Arcade Trade Script
vendor website.

This awesome script (version 1.0 beta) has a XSS vulnerability in one
of it’s variables, this attack could be used to grab peoples cookies
or to launch denial of service attacks.

PoC:
index.php?a=gamelist&q=[XSS]&submit=GO

The vendor was really fast, about a couple of hours, to patch it after
I mailed him so just upgrade to a new version to have it fixed.
It’s always nice to see an admin who cares and answer positively to a
possible security threat.