Cross-site scripting (XSS) vulnerability in index.php in Don Barnes DRBGuestbook 1.1.13 allows remote attackers to inject arbitrary web script or HTML via the action parameter.
https://exchange.xforce.ibmcloud.com/vulnerabilities/36931
http://www.securityfocus.com/bid/25911
http://www.securityfocus.com/archive/1/481417/100/0/threaded
http://securityreason.com/securityalert/3190