source: http://www.securityfocus.com/bid/11985/info

MediaWiki is reported prone to a vulnerability that can allow a remote attacker to upload arbitrary PHP scripts to a vulnerable server. This issue results from insufficient sanitization of user-supplied input.

If successful, the attacker can execute arbitrary script code on a vulnerable server. This can lead to unauthorized access in the context of the application.

MediaWiki 1.3.8 and prior versions are affected by this issue. 

Script file name:
attack.php.rar