https://www.cnet.com/news/facebook-breach-affected-50-million-people/

While access tokens aren't your password, they allow people to log into accounts without needing it. As a precautionary measure, Facebook logged about 90 million people out of their accounts, the company said.

The social network said it discovered the attack earlier this week and informed law enforcement. The company said the investigation is in the early stages and Facebook does not yet know who was behind the attacks.