The PPWP – Password Protect Pages WordPress plugin before version 1.9.11 allows to put the site content behind a password authorization, however users with subscriber or greater roles can view content via the REST API.
The PPWP – Password Protect Pages plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 1.8.9 via API. This makes it possible for unauthenticated attackers to obtain post titles, IDs, slugs as well as other information including for password-protected posts.