Sebastian Fischer

The actions linked in the emails of the extension (e.g. to confirm a registration or the deletion of an account) do not reject requests with a missing or invalid hash. Instead, the frontend user given in the request is used. Unauthenticated attackers can therefore perform these actions for arbitrary active frontend users. This allows them to retrieve the email address or username of all frontend users and to delete arbitrary frontend user accounts.

The create and edit flows fail to restrict submitted user properties and do not enforce access control on frontend user group assignments. This allows an attacker to assign an arbitrary frontend user group to a newly registered or edited account, leading to unauthorized access to content and functionality reserved for privileged frontend user groups.