The WPS Hide Login plugin for WordPress is vulnerable to Login Page Disclosure in all versions up to, and including, 1.9.15.2. This is due to a bypass that is created when the 'action=postpass' parameter is supplied. This makes it possible for attackers to easily discover any login page that may have been hidden by the plugin.
https://plugins.trac.wordpress.org/changeset/3099109/wps-hide-login