Discuz! 4.0 rc4 does not properly restrict types of files that are uploaded to the server, which allows remote attackers to execute arbitrary commands via a filename containing ".php.rar" or other multiple extensions that include .php.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2005-2615
http://www.securityfocus.com/bid/14564
http://securitytracker.com/id?1014673
http://secunia.com/advisories/16433
http://archives.neohapsis.com/archives/fulldisclosure/2005-08/0440.html