Facebook just disclosed that attackers took advantage of a security issue to attack its systems, and almost 50 million accounts are affected.
The flaw, discovered on Tuesday, allowed attackers to take over Facebook users' accounts. The company's stock dropped 3% on the news.
"Our investigation is still in its early stages. But it's clear that attackers exploited a vulnerability in Facebook's code...."
https://www.businessinsider.com/facebook-security-attack-affecting-50-million-users-2018-9