Up to 50 million accounts were breached by hackers, Facebook has admitted.
Facebook chief executive Mark Zuckerberg said engineers discovered the breach on Tuesday, and patched it on Thursday night.
“We don’t know if any accounts were actually misused,” Zuckerberg said. “We face constant attacks from people who want to take over accounts or steal information around the world.”
Facebook reset the 50 million breached accounts, meaning users will need to sign back in using passwords. It also reset “access tokens” for another 40 million accounts as a precautionary measure.