Facebook now says up to 87 million users' data improperly shared The Facebook update comes as CEO Mark Zuckerberg agrees to testify to Congress.

The revelation Wednesday came in a Facebook release that detailed new plans to restrict data access and shortly after word that CEO Mark Zuckerberg has agreed to testify before a House panel next week – heeding calls from lawmakers to explain Facebook’s role in the 2016 election and subsequent privacy crisis.

In a rare call with reporters Wednesday afternoon, Zuckerberg was contrite. "It’s clear now that we didn't do enough at preventing abuse," he said, adding, "We didn't take a broad enough view of what our responsibilities were. That was a huge mistake. It was my mistake."

Zuckerberg conceded he was "too flippant" in referring to potential problems in the 2016 election year as "crazy" and when asked why Facebook wasn't doing audits all along he said, "Knowing what I know today, we should've done more and we will."

"I wish that I could snap my fingers and in three months or six months have solved these issues," he said, adding he thinks fixing privacy concerns will be "a multi-year effort."

The House Energy and Commerce Committee announced earlier Wednesday that Zuckerberg will testify in person on April 11. Late Wednesday, the Senate Judiciary and Commerce committees announced a joint hearing with Zuckerberg next Tuesday, April 10.

Lawmakers want Zuckerberg to explain reports that Cambridge Analytica allegedly misused Facebook data from user profiles. Cambridge Analytica did work for the Trump campaign during the 2016 presidential election, but a spokesperson for the Trump campaign told ABC News in a statement that the campaign used the RNC for its voter data and not Cambridge Analytica.

“Using the RNC data was one of the best choices the campaign made. Any claims that voter data were used from another source to support the victory in 2016 are false,” the statement said.

Cambridge Analytica did not respond to ABC News’ attempts Wednesday to get comment on Zuckerberg agreeing to appear before the committee, but did issue a new statement responding to Facebook’s user data announcement. In its statement, Cambridge Analytica pushed back on the new figure of 87 million and shifted blame to a third party research firm.

“Cambridge Analytica licensed data for no more than 30 million people from GSR, as is clearly stated in our contract with the research company. We did not receive more data than this,” the statement said, adding, “Our contract with GSR stated that all data must be obtained legally, and this contract is now a matter of public record. We took legal action against GSR when we found out they had breached this contract.”

"GSR" refers to Global Science Research, the firm founded by Aleksandr Kogan, the Cambridge University researcher who collected information on millions of Americans through Facebook for Cambridge Analytica.

“We did not use any GSR data in the work we did in the 2016 US presidential election,” the statement added.

In the meantime, the Federal Trade Commission announced last month that it had opened its own investigation looking into whether the tech giant violated a 2011 consent decree it signed with the FTC promising to protect users’ privacy.

On Tuesday, Facebook announced it had removed dozens of additional Facebook and Instagram accounts tied to a Russian organization called the Internet Research Agency, which spread disinformation online in the U.S. before the 2016 election according to the Treasury Department.

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“This hearing will be an important opportunity to shed light on critical consumer data privacy issues and help all Americans better understand what happens to their personal information online,” said committee chairman Rep. Greg Walden, R-Ore., and ranking member Rep. Frank Pallone Jr., D-N..J., in a joint statement announcing Zuckerberg’s appearance.

“We appreciate Mr. Zuckerberg’s willingness to testify before the committee, and we look forward to him answering our questions on April 11th,” Walden and Palone wrote.

Zuckerberg’s announced testimony before House Energy and Commerce is his first confirmed appearance ever in front of a congressional committee, although a Facebook spokesperson told ABC News that “conversations with other committees continue” about additional appearances on Capitol Hill. The embattled billionaire businessman has received requests from the Senate Commerce Committee and Senate Judiciary Committee – which invited him to appear on April 10 – and the Senate Select Committee on Intelligence has said it intends to extend an invitation as well.

Senate panel sets April 10 for Facebook CEO to testify

Government panels in the UK, Australia, and beyond have also requested Zuckerberg to appear. Zuckerberg recently declined an invitation from a British Parliamentary committee investigating the rise of “fake news,” but offered to send two of his deputies instead.

Last month, Facebook sent a handful of senior staff to brief aides to a number of key Senate and House committees on privacy concerns.

“These tech platforms who are extraordinarily powerful who’ve been great iconic American success stories - they need to be more forthcoming or Washington is going to start imposing rules and regulations that may not fit,” warned Sen. Mark Warner, D-Va., vice chairman of the Intelligence Committee and, himself, a former tech industry entrepreneur and investor.