The Drupal Team reports:
Visiting a specially crafted page, anywhere on the web, may allow that page to post forms to a Drupal site in the context of the visitor's session. To illustrate; suppose one has an active user 1 session, the most powerful administrator account for a site, to a Drupal site while visiting a website created by an attacker. This website will now be able to submit any form to the Drupal site with the privileges of user 1, either by enticing the user to submit a form or by automated means. An attacker can exploit this vulnerability by changing passwords, posting PHP code or creating new users, for example. The attack is only limited by the privileges of the session it executes in.