Directory traversal vulnerability in Advanced Guestbook 2.4.2 allows remote attackers to bypass .htaccess settings, and execute arbitrary PHP local files or read arbitrary local templates, via a .. (dot dot) in a lang cookie, followed by a filename without its .php extension, as demonstrated via a request to index.php.
https://exchange.xforce.ibmcloud.com/vulnerabilities/34152
http://www.vupen.com/english/advisories/2007/1726
http://www.securityfocus.com/archive/1/467941/100/0/threaded
http://www.securityfocus.com/archive/1/467937/100/0/threaded
http://www.netvigilance.com/advisory0013
http://www.netvigilance.com/advisory0012