Grav: Privilege Escalation via Missing Server-Side Validation of groups/access

Grav is a file-based Web platform. Prior to 2.0.0-beta.2, the Login::register() method in the Login plugin accepts attacker-controlled groups and access fields from the registration POST data without server-side validation. When registration is enabled and groups or access are included in the configured allowed fields list, an unauthenticated user can self-register with admin.super privileges by injecting these fields into the registration request. This vulnerability is fixed in 2.0.0-beta.2.