Facebook CEO Mark Zuckerberg is set to give public testimony Tuesday before a group of U.S. senators after apologizing for the way his company handled data for millions of users.
He is due to appear before a joint hearing of the Senate Judiciary Committee and Senate Commerce Committee, and on Wednesday will go before House lawmakers.
Judiciary Committee Chairman Chuck Grassley said users “deserve to know how their information is shared and secure,” and that he wants to explore with Zuckerberg ways to balance safety with innovation.
WATCH: Facebook data breach
Zuckerberg met privately with lawmakers in Washington on Monday and released written testimony saying the social media network should have done more to prevent itself and the data of its members from being misused.
“We didn’t take a broad enough view of our responsibility, and that was a big mistake. It was my mistake, and I’m sorry,” Zuckerberg said.
In his statement, Zuckerberg said Facebook is starting to notify 87 million users whose personal data was harvested without their knowledge by Cambridge Analytica, the British voter profiling company U.S. President Donald Trump’s campaign hired to target likely supporters in 2016.
Facebook believes most of the affected users, more than 70 million, are in the United States, but there are more than a million each in the Philippines, Indonesia and Britain.
Facebook allowed a British researcher to create an app on Facebook on which about 200,000 users divulged personal information that academic Alexsandr Kogan subsequently shared with Cambridge Analytica. The number of affected users multiplied exponentially, however, because of the data collected from all the friends, relatives and acquaintances the 200,000 users had contact with on Facebook.
Cambridge Analytica says it only had data for 30 million Facebook users.
Senator Bill Nelson, the top Democrat on the Senate Commerce Committee, said Monday that Zuckerberg told the him that the company was “lied to” by Cambridge Analytica.
Nelson said he felt Zuckerberg was honest with him during their private meeting, but said Facebook faces many challenges in the future.
“If we don’t watch out with social media and platforms, like Facebook, and the mistakes that they made in the past, then no American is going to have any privacy anymore,” Nelson said.
Facebook said it is sending a notice to all of its 2.2 billion users with a link to see what apps they use and instructions on how they can, if they wish, shut off third-party access to their apps.