VVertex Password Protect CPTs adds a password field to the editor for public WordPress post types.
When a password is configured, visitors who open that singular item on the front end must enter the correct password before the page is rendered.
The plugin protects direct singular front-end requests handled by the normal WordPress template flow. It does not attempt to restrict data exposed separately through custom REST endpoints, custom API integrations, feeds, archives, search implementations, or third-party code.