PHP remote file inclusion vulnerability in index.php in Gaestebuch 1.5 allows remote attackers to execute arbitrary PHP code via a URL in the config[root_ordner] parameter.
http://www.vupen.com/english/advisories/2007/2837
http://www.securityfocus.com/archive/1/475950/100/0/threaded
http://securityreason.com/securityalert/2994