Cross-site scripting (XSS) vulnerability in Matt Wright Guestbook 2.3.1 allows remote attackers to execute arbitrary web script or HTML via the (1) Your Name, (2) E-Mail, or (3) Comments fields when posting a message.
https://exchange.xforce.ibmcloud.com/vulnerabilities/25697
http://www.vupen.com/english/advisories/2006/1287
http://www.securityfocus.com/bid/17438
http://www.securityfocus.com/archive/1/430356/100/0/threaded