The Browse As plugin for WordPress is vulnerable to authentication bypass in versions up to, and including, 0.2. This is due to incorrect authentication checking in the IS_BA_Browse_As::notice function with the is_ba_original_user_COOKIEHASH cookie value. This makes it possible for authenticated attackers, with subscriber-level permissions and above, to log in as any existing user on the site, such as an administrator, if they have access to the user id.
The product requires authentication, but the product has an alternate path or channel that does not require authentication.