Within the next 24 hours, Facebook CEO Mark Zuckerberg will speak publicly about "rebuilding trust" amid allegations that data from more than 50 million Facebook users was misused by Cambridge Analytica, according to NBC News.

The social-networking giant disclosed late Friday that researchers from Cambridge Analytica, a UK-based data analytics firm affiliated with the Donald Trump presidential campaign, had duped the company to gain access to data through an app called "thisisyourdigitallife," which was used for political ads during the 2016 US presidential election. 

While Facebook said in a statement that it had banned the group, there's been mounting pressure on Zuckerberg to testify before Congress and to explain why the company didn't tell the public that data had been used in violation of its terms of service when it found out in 2015. The hashtag "#WheresZuck" started appearing on Twitter in reference to Zuckerberg's lack of a public appearance or statement.

The Cambridge Analytica scandal is the latest in a series of online controversies involving the 2016 US presidential election. Twitter, Reddit, Facebook and other platforms appear to have been manipulated by automated bot programs and operatives working for the Russian government. The misinformation campaign is being investigated by the FBI and the US Senate.

The Trump campaign hired Cambridge Analytica, which helps political campaigns reach potential voters online, to run data operations during the 2016 election. The firm combines data from multiple sources to create "profiles" of users, then uses computer programs to predict voter behavior and try to influence voters with specialized ads. 

Cambridge Analytica released a statement Monday calling the claims against its company "false allegations."

US senators, including Minnesota Democrat Amy Klobuchar, Louisiana Republican John Kennedy and Virginia Democrat Mark Warner, have called for Zuckerberg to testify before Congress. The Federal Trade Commission is reportedly looking into the matter. 

The European Union also launched an investigation into Cambridge Analytica and Facebook. Damian Collins, the chair of Parliament's Digital, Culture, Media and Sport Committee in the UK, sent a letter to Zuckerberg Tuesday requesting he appear to offer "oral evidence" on Facebook's handling of user data. 

Facebook did not immediately respond to a request for comment.

First published March 21 at 7:54 a.m. PT. 
Update, 8:49 a.m. PT: Adds background. 

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