Facebook founder and CEO Mark Zuckerberg’s phone number was included in the the personal data of 533 Mln users of the social media platform, which was leaked by hackers on Saturday.
Facebook co-founders Chris Hughes and Dustin Moskovitz were also among those included in the database.
The phone numbers in the leaked database are reported to be matching the real ones.
The database appears on the internet for free on Saturday, but before that hackers traded information for a small fee.
Facebook has brushed off the reports of the leak in a statement, saying that the data is old and that Facebook addressed the exploit in August 2019.
The leak reportedly affected more than 32 million users in the United States, more than 11 million in the United Kingdom, and millions in more than a hundred other countries.
According to Alon Gal, chief technical officer of cybercrime intelligence firm Hudson Rock, which detected the leak, the information could be used by fraudsters for identity theft or phishing scams.
Facebook has been struggling to win back users’ trust in recent years amid data privacy issues. In 2018, it was revealed that Facebook had exposed the personal data of around 87 million users to a British data analysis firm, Cambridge Analytica, violating its users’ trust and privacy. The people had their personal information collected and used, most without their knowledge or consent, by companies intending on helping candidates tailor their political message in stump speeches city-by-city, based on user data bought from Facebook.
A probe by the UK's Information Commissioner's Office found Cambridge Analytica had not acted illegally, but the FTC issued Facebook a $5 billion fine in 2019 over its data mining for profit.