The Advanced Custom Fields: Extended WordPress plugin before 0.9.2.8, Advanced Custom Fields: Extended PRO WordPress plugin before 0.9.2.8 does not verify that the requester is authorised to edit the targeted user account in the update-user action of its front-end Forms module, performing that check only when the target account holds an administrator role, which allows unauthenticated visitors to overwrite any non-administrator account's credentials and obtain a session for that account. Exploitation requires the site to publish a form whose user-update action maps its target to a visitor-submitted value rather than to the default current user.