Free Movies Box has been updated to version 22.214.171.124 (Windows 8) and 126.96.36.199 (Windows 8.1).
SHARE ON FACEBOOK option was added. Now you can show the movie you are watching to your (Facebook) friends!
Download latest version from here: http://apps.microsoft.com/windows/app/free-movies-box/30e55063-2c47-49a7-a99d-26bc87466d47.
Or just update your app if you have it already installed.