Plone CMS before 3 places a base64 encoded form of the username and password in the __ac cookie for all user accounts, which makes it easier for remote attackers to obtain access by sniffing the network.

Plone CMS 3.0.5, and probably other 3.x versions, places a base64 encoded form of the username and password in the __ac cookie for the admin account, which makes it easier for remote attackers to obtain administrative privileges by sniffing the network.

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.

Plone CMS 3.x uses invariant data (a client username and a server secret) when calculating an HMAC-SHA1 value for an authentication cookie, which makes it easier for remote attackers to gain permanent access to an account by sniffing the network.

Multiple cross-site request forgery (CSRF) vulnerabilities in Plone CMS 3.0.5 and 3.0.6 allow remote attackers to (1) add arbitrary accounts via the join_form page and (2) change the privileges of arbitrary groups via the prefs_groups_overview page.