cookiedecode function in PHP-Nuke 4.4 allows users to bypass authentication and gain access to other user accounts by extracting the authentication information from a cookie.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6183
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-0001
http://archives.neohapsis.com/archives/bugtraq/2001-02/0257.html