Facebook has revealed that its team discovered a security breach last week that exposed almost 50 million accounts.
The 'View As' feature - that shows what your account looks like to the public - had vulnerability in its code, which allowed hackers to break in.
Facebook said it has turned off the feature for now and has reset those 50 million accounts and another 40 million just to be safe.
The social media giant said it doesn't know who is behind the attack and hasn't figured out if any of these accounts were misused.