Facebook on Friday said hackers accessed personal data of 29 million users in a breach at the world's leading social network disclosed late last month.
The company had originally said up to 50 million accounts were affected in a cyberattack that exploited a trio of software flaws to steal "access tokens" that enable people to automatically log back onto the platform.
"We now know that fewer people were impacted than we originally thought," Facebook vice president of product management Guy Rosen said in a conference call updating the investigation.
The hackers—whose identities are still a mystery—accessed the names, phone numbers and email addresses of 15 million users, he said.
For another 14 million people, the attack was potentially more damaging.
Facebook said cyberattackers accessed that data plus additional information including gender, religion, hometown, birth date and places they had recently "checked in" to as visiting.
No data was accessed in the accounts of the remaining one million people whose "access tokens" were stolen, according to Rosen.
The attack did not affect Facebook-owned Messenger, Messenger Kids, Instagram, WhatsApp, Oculus, Workplace, Pages, payments, third-party apps or advertising or developer accounts, the company said.