admin/options.php in Stephen Craton (aka WiredPHP) Chatness 2.5.3 and earlier does not check for administrative credentials, which allows remote attackers to read and modify the classes/vars.php and classes/varstuff.php configuration files via direct requests.
http://www.vupen.com/english/advisories/2007/1386
http://www.securityfocus.com/archive/1/465547/100/0/threaded