Group of hackers exploited a zero-day vulnerability in its social media that permit them to steal secret access tokens for millions accounts. It gives them access to private information without requirement of account password or validating two-factor authentication code. Secret access tokens equal to digital keys that maintain users logged in to Facebook, so they don’t have to retype their credentials anytime they use the app. The vulnerability resided in the “View As” feature, which allows users to find out what other Facebook users would see if they visit your profile. If you logged out automatically from your Facebook, you are one of the millions that are hacked and you are not alone. Check your setting, locations, and find out who is logging to your Facebook and delete them, it will disable them temporary and change your password.