Interpretation conflict in includes/mainfile.php in PHP-Nuke 7.9 and later allows remote attackers to perform cross-site scripting (XSS) attacks by replacing the ">" in the tag with a "<", which bypasses the regular expressions that sanitize the data, but is automatically corrected by many web browsers.  NOTE: it could be argued that this vulnerability is due to a design limitation of many web browsers; if so, then this should not be treated as a vulnerability in PHP-Nuke.