WooCommerce Order Proposal <= 2.0.5 - Authenticated (Shop Manager+) Privilege Escalation via Order Proposal

The WooCommerce Order Proposal plugin for WordPress is vulnerable to privilege escalation via order proposal in all versions up to and including 2.0.5. This is due to the improper implementation of allow_payment_without_login function. This makes it possible for authenticated attackers, with Shop Manager-level access and above, to log in to WordPress as an arbitrary user account, including administrators.