Do you know your Facebook account has 3 passwords? Read more about it here: http://www.labnol.org/internet/facebook-account-passwords/21241/. TL;DR: if your password is "passWORD". You can log into your account with "PASSword" or "PassWORD". This is done because so many people left their CAPSLOCK when they type in the password. So, this add-on will check the reversed-case password and the uncapitalized-first-letter password and let user login if they are matched.
A little bit about the technique: password are still stored the same way by XenForo (so you can disable/uninstall this add-on anytime if you don't like it, etc.). This add-on generates the extra passwords from inputed password (when user press the Login button in the login form).
1. Upload files and directories inside `upload` to XenForo's root directory.
2. Import the .xml file using XenForo add-on importer
3. Now log out and try to log in back!