An open redirect on the login form (and possibly other places) in Plone 4.0 through 5.2.1 allows an attacker to craft a link to a Plone Site that, when followed, and possibly after login, will redirect to an attacker's site.

The PlonePAS product 3.x before 3.9 and 3.2.x before 3.2.2, a product for Plone, does not properly handle the login form, which allows remote authenticated users to acquire the identity of an arbitrary user via unspecified vectors.