Facebook CEO Mark Zuckerberg said Wednesday the estimate of 50 million users whose data was breached in the Cambridge Analytica debacle was "conservative" and he would testify before Congress "if it's the right thing to do."
"We're going to be even conservative on that," Zuckerberg told Laurie Segall on CNN. "We may not have all of the data in our system today.
"So, anyone whose data might have been affected by this, we're going to make sure that we tell.
"And going forward, when we identify apps that are similarly doing sketchy things, we're going to make sure that we tell people then.
"That's definitely something that, looking back on this, I regret that we didn't do at the time," Zuckerberg said. "I think we got that wrong.
"We're committed to getting that right going forward."
Zuckerberg has been under fire since news reports Cambridge Analytica obtained the data of as many as 50 million Facebook users without their knowledge or consent — and information was ultimately obtained by the Trump campaign during the 2016 presidential election.
Facebook's stock has plunged, costing the company millions of dollars, and more than 40,000 people have mentioned the #DeleteFacebook hashtag on Twitter on Tuesday.
Zuckerberg broke his silence Wednesday with a lengthy Facebook post that admitted mistakes but offered no apology.
He did not apologize in the interview with CNN's Segall, though he said he would testify to Congress "if it's the right thing to do."
"Facebook testifies in Congress regularly," Zuckerberg said, and he would only appear if he is the person "who will have the most knowledge about what Congress is trying to learn."
On regulating Facebook and other Internet properties, Zuckerberg said: "I actually am not sure we shouldn't be regulated.
"In general, technology is an increasingly important trend in the world, and I actually think the question is more 'What is the right regulation?'
"If you look at how much regulation there is around advertising on TV, in print, it's just not clear why there should be less on the Internet," he said. "You should have the same level of transparency required."