The RingCentral Communications plugin for WordPress is vulnerable to Authentication Bypass due to improper validation within the ringcentral_admin_login_2fa_verify() function in versions 1.5 to 1.6.8. This makes it possible for unauthenticated attackers to log in as any user simply by supplying identical bogus codes.
https://wordpress.org/plugins/rccp-free/#developers
https://plugins.trac.wordpress.org/changeset/3349361/
https://plugins.trac.wordpress.org/browser/rccp-free/tags/1.6.8/ringcentral.php