source: https://www.securityfocus.com/bid/6033/info

A vulnerability has been discovered in gBook v1.4.

It has been reported that it is possible for an unauthorized attacker to gain administrative access to gBook by passing a malicious request to a php script.

Exploiting this issue could allow unauthorized attackers to execute arbitrary administrative actions against the target guestbook, such as corrupt valid user supplied entries. 

http://[Target]/gb/index.php?login=true