The cross-site request forgery (CSRF) protection in PHP-Nuke 8.0 and earlier does not ensure the SERVER superglobal is an array before validating the HTTP_REFERER, which allows remote attackers to conduct CSRF attacks.
http://www.securityfocus.com/archive/1/462727/100/0/threaded
http://www.securityfocus.com/archive/1/462575/100/0/threaded
http://www.securityfocus.com/archive/1/462308/100/100/threaded