John Blackbourn

If you publish many password protected posts (or even if you don’t), you may end up using the same password for each one. With this plugin you can define a global password from your ‘Settings -> Global Post Password’ menu, and switch password protection on or off from the writing screen with just one click. Whenever you change the global password, all password protected posts are automatically updated with the new password.
Now whenever you write or edit a post or page you’ll be able to switch password protection on or off with one click, instead of having to manually type in a password each time. You can change the global password whenever you like from the ‘Settings -> Global Post Password’ menu.
Note that this plugin does not automatically enable password protection on every post. It allows you to use a global password for every post that you choose to password protect.
Please note that this plugin is no longer actively maintained. The global post password setting does not work with the block-based editor in WordPress and it’s unlikely that I’ll add support for it unless someone else volunteers to develop it. It does work with the “Classic” editor and with versions of WordPress prior to 5.0.

Global Post Password

Globally set a password for all password protected posts and pages.

Sidecar TV, Plugin Developers

This will protect the user or admin facing wordpress pages. Separate login and passwords can be setup for each.
This isn’t anything fancy, not super secure, just basic and easy. It is called simple after all.

Simple Privacy

A simple way to create a private Wordpress blog with htauth.

Global Post Password vs Simple Privacy