source: https://www.securityfocus.com/bid/5865/info

MySimpleNews allows users to enter news articles through a web interface. It will allow PHP code to be injected into URI parameters of the 'users.php' script, which will be stored into a MySimpleNews file (news.php3). The injected code may then be executed by the attacker by requesting the 'news.php3' script.

http://[target]/users.php?LOGIN=[PHP code]

http://[target]/users.php?DATA=[PHP code]

http://[target]/users.php?MESS=[PHP code]

PHP code injected in this manner can be executed with the following request:

http://[target]/news.php3