source: http://www.securityfocus.com/bid/8896/info

It has been reported that Chi Kien Uong Guestbook may be prone to a cross-site scripting vulnerability that may allow a remote attacker to execute HTML or script code in a user's browser. The problem is reported to present itself due to insufficient sanitization of user-supplied data when posting an e-mail address or URL to the site. It has been reported that double quotes are not filtered therefore an attacker may be able to append malicious script code in order to be executed on a victim's web browser.

Successful exploitation of this attack may allow an attacker to steal cookie-based authentication information.

" onmouseover="alert(document.cookie) 