An incomplete fix for a cross-site scripting (XSS) vulnerability in SquirrelMail 1.2.8 calls the strip_tags function on the PHP_SELF value but does not save the result back to that variable, leaving it open to cross-site scripting attacks.
http://www.securityfocus.com/bid/7019
http://www.redhat.com/support/errata/RHSA-2003-042.html
http://www.iss.net/security_center/static/10634.php
http://www.debian.org/security/2002/dsa-191