datarumx

This WordPress plugin allows you to block access to static pages by one or more security questions. First, you have to create and add some questions with answers to the main list. Answers are case insensitive. Then, associate questions from list you created with pages you need to block. After question is associated with a page – page becomes blocked until user provides correct answers on questions associated with a page, if he does – access will be granted during current session.

Pageblocker "Seeya"

This plugin allows you to block access to static pages by one or more security questions.

KaeruCT

This plugin allows passwords for password-protected pages/posts to be passed directly through the URL.
The query string parameter that should contain the password is <code>pw</code>.
For example, if the URL of your post is <code>http://myblog.com/password-protected-page/</code> and the password is <code>PASSWORD</code>, 
then just append <code>?pw=PASSWORD</code> to it.
If the URL already contains a query string (for example, <code>http://myblog.com/?p=5</code>), then be sure to append <code>&pw=PASSWORD</code> instead.

Password Passthrough

This plugin allows passwords for password-protected pages/posts to be passed directly through the URL.

Pageblocker "Seeya" vs Password Passthrough