source: https://www.securityfocus.com/bid/13557/info

PHP Nuke is prone to an input validation vulnerability. Reports indicate the script fails to correctly identify potentially dangerous characters when the characters are double hex-encoded (i.e. %25%41 == %41 == A).

A remote attacker may exploit this issue to bypass PHP Nuke protections and exploit issues that exist in the underlying PHP Nuke installation. 

Will be filtered:
'modules.php?FistFucker=()'

Will be bypassed:
'modules.php?FistFucker=%2528%2529'


Will be filtered:
'/**/UNION/**/SELECT/**/'

Will be bypassed:
'/%2A%2A/UNION/%2A%2A/SELECT/%2A%2A/'