source: www.securityfocus.com/bid/26318/info

PHP Helpdesk is prone to a local file-include vulnerability because it fails to properly sanitize user-supplied input.

Exploiting this issue may allow an unauthorized user to view files and execute local scripts.

PHP Helpdesk 0.6.16 is vulnerable to this issue; other versions may also be affected. 

http://www.example.com/index.php?whattodo=../../../../../../../../../../../etc/passwd%00