Ayesh Karunaratne

This plugin ensures that when users of your website (including site administrators), the browsers are instructed to clear all residue such as cookies and caches to enhance the security.
<a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Clear-Site-Data" rel="nofollow ugc"><code>Clear-Site-Data</code> HTTP header</a> is sent when a user logs out, which supported browsers will react by removing all existing cookies, cache, and other storage. It will not remove saved passwords, permissions, adblocker rules, and other data that are supposed to be permanent.
This plugin prevents possible security vulnerabilities such as clicking the “Back” button in the browser after logging out revealing the pages that should not have been accessible after logging out. Furthermore, this cleans the browser cache, which prevents accessing authenticated media assets (such as purchased images) from the browser cache of a victim.

Clear Logout

A tiny WordPress plugin to clear all browser data related to the site upon logout (With Clear-Site-Data header).

Nate Reist

This plugin simply adds a logout button to the content of any password protected post. Sometimes clients want a password protected page to share information with privileged individuals and the default 10 days for the cookie to expire is too long for their liking. So I wrote a little plugin to do this with AJAX and set the cookie to expire immediately, well actually 10 days in the past.
<ul>
<li>Works logged in or out as a WordPress user.</li>
<li>Uses the same functionality WordPress uses to set post cookies.</li>
<li>Has a simple settings page to make everything easier.</li>
<li>Allows you to alert user they have logged out.</li>
</ul>

Protected Posts Logout Button

Automatically adds a logout button to your password protected content.

Clear Logout vs Protected Posts Logout Button