Cross-site scripting (XSS) vulnerability in index.php in iPei Guestbook 1.7 allows remote attackers to inject arbitrary web script or HTML via the email parameter, as used by the email field, when signing a guestbook.
https://exchange.xforce.ibmcloud.com/vulnerabilities/23914
http://www.securityfocus.com/bid/16092
http://secunia.com/advisories/18241
http://pridels0.blogspot.com/2005/12/ipei-guestbook-xss-vuln.html