Following the reveal in March that a data analytics firm with ties to Donald Trump's presidential campaign exploited the private data of more than 50 million Facebook users, Zuckerberg went on a media tour in which he called the incident "a major breach of trust". He also is to testify Wednesday before the House Energy and Commerce Committee.
A full transcript of the hearing is available on the Washington Post website.
When questioned by California Senator Kamala Harris about why Facebook did not notify users when the network discovered Cambridge Analytica's data, he responded that "it was a mistake" that they didn't let users know and that "there's a lot of things [they] should have done differently". "I started Facebook, I run it, and I'm responsible for what happens here". "This includes the basic responsibility of protecting people's information, which we failed to do with Cambridge Analytica".
While congressional lawmakers pummeled Zuckerberg with questions ranging from Facebook's negligence in curtailing violence-inciting messages in Myanmar to the Cambridge Analytica scandal, the company's stock surged, closing Tuesday up 4.5% at $165.04 per share.
It came as Zuckerberg admitted his slow reaction to Russian meddling in the United States election was "one of my greatest regrets" in a blockbuster Senate hearing.
"Whether is was ads placed on Facebook - potentially from foreign countries, what's going to be put in place for the midterm elections to make sure we have gotten to the bottom of this and are taking corrective actions", said Baldwin.
"Um... no", Zuckerberg said after pausing, then smiled as the room laughed.
Users could have had their data compromised either because they logged into the app on their own account, or one of their friends did so. In addition to saying he is sorry, Zuckerberg outlined the steps the company has taken to restrict outsiders' access to people's personal information.
Mr Zuckerberg was answering questions in the wake of the Cambridge Analytica data collection scandal.
Zuckerberg met Monday with Florida Sen. Republicans have yet to get behind any such legislation, but that could change.
"Your right to privacy, the limits of your right to privacy, and how much you'd give away in modern America". Soon after Facebook was hit by the controversy, the company has made a decision to reward people who report any misuse by app developers.