Facebook says hackers accessed a wide swath of information - ranging from emails and phone numbers to more personal details like sites visited and places checked into - from millions of accounts as part of a security breach the company disclosed two weeks ago.
Twenty-nine million accounts had some form of information stolen. Originally Facebook said 50 million accounts were affected, but that it didn't know if they had been misused.
On Friday Facebook said hackers accessed names, email addresses or phone numbers from these accounts. For 14 million of them, hackers got even more data, such as hometown, birthdate, the last 10 places they checked into or the 15 most recent searches.
An additional 1 million accounts were affected, but hackers didn't get any information from them.
The company says it will be sending customized messages to people affected. The attackers were able to steal what are called "access tokens" - which are like digital keys that keep people logged in so they don't need to keep re-entering their password.