Plone CMS does not record users' authentication states, and implements the logout feature solely on the client side, which makes it easier for context-dependent attackers to reuse a logged-out session.
https://exchange.xforce.ibmcloud.com/vulnerabilities/41423
https://euvd.enisa.europa.eu/vulnerability/EUVD-2008-1400
http://www.securityfocus.com/archive/1/489544/100/0/threaded