https://wccftech.com/facebook-massive-security-hack/

Facebook says the security breach that rattled users last month impacted fewer people than initially believed. It’s still in millions of users but down to 30 million from 50 million users who were originally expected to be impacted.

In a post earlier today, the company said that the attackers exploited a vulnerability in Facebook’s code that existed between July 2017 and September 2018. This vulnerability in the code of View As (a feature that allows you to see how their profile looks to a specific set of people) enabled hackers to get access to a digital token that was used to log into millions of user accounts.