SQL injection vulnerability in index.php in @lex Guestbook 4.0.2 and earlier, when magic_quotes_gpc is disabled, allows remote attackers to execute arbitrary SQL commands via the lang parameter.
https://www.exploit-db.com/exploits/3103
https://exchange.xforce.ibmcloud.com/vulnerabilities/31393
http://www.vupen.com/english/advisories/2007/0137
http://www.securityfocus.com/bid/21926
http://www.securityfocus.com/archive/1/456218/100/0/threaded
http://securityreason.com/securityalert/2135