A white hat hacker has proven how easy it is to hack multiple Facebook accounts with some basic computer skills. Facebook has patched the bug after been reported by a hacker. Facebook provides you an extra layer of security to protect your account against such attacks. Facebook also provides a security feature that sends an email or SMS alert to your phone if an unauthorized user is accessing your account from a remote device, or a different web browser, to prevent this kind of attacks. The social network uses an algorithm that generates a random 6-digit passcode that does not change until gets used.
Source: https://thehackernews.com/2016/08/hack-facebook-account.html