If you use any of the following scripts:
FA-PHPHosting
PHPClique
PHPCalendar
PHPCurrently
PHPFanBase
PHPQuotes
Please disable them immediately or use the fix specified below. There are serious exploits going around the net right now and have been for the past few months. All of these scripts are made by
http://codegrrl.com/ and have a ridiculously easy hole in them:
"

include($logout_page);
"
This allows an attacker to include whatever code they wish into the php file and run the commands.
To avoid getting your site defaced, we recommend you either remove the
protection.php file asap, or edit it and remove that line above.