The bbPress plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 2.6.11. This is due to missing or incorrect nonce validation on the bbp_user_add_role_on_register() function. This makes it possible for unauthenticated attackers to elevate their privileges to that of a bbPress Keymaster via a forged request granted they can trick a site administrator into performing an action such as clicking on a link. Rather than implementing a nonce check to provide protection against this vulnerability, which would break functionality, the plugin no longer makes it possible to select a role during registration.
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.