Zuckerberg said there was a "breach of trust" involving Cambridge Analytica, Facebook and a Cambridge University researcher named Aleksandr Kogan, who created an app to collect data that was later shared with Cambridge Analytica.
"But it was also a breach of trust between Facebook and the people who share their data with us and expect us to protect it. We need to fix that," he wrote.
Zuckerberg said Facebook will restrict third-party developers from accessing data beyond names, profile photos and email addresses. The company will also require developers to sign a contract before asking Facebook users for access to their posts or other private data. Users will also see a tool at the top of their news feeds showing the what apps they have used and will have an easy way to revoke the apps' access to their data.
"I started Facebook, and at the end of the day I'm responsible for what happens on our platform. I'm serious about doing what it takes to protect our community. While this specific issue involving Cambridge Analytica should no longer happen with new apps today, that doesn't change what happened in the past. We will learn from this experience to secure our platform further and make our community safer for everyone going forward."
Sen. Richard Blumenthal, D-Conn., a member of the Senate Judiciary and Commerce Committees, said he was not satisfied with Zuckerberg's statement, calling it "damage control."
Blumenthal told NPR's Ailsa Chang on "All Things Considered":
"This very superficial mea culpa makes even more necessary his appearing before the committee. He has to be questioned, perhaps under oath. Documents need to be subpoenaed. We need to know how Facebook is going to really protect privacy if it continues with the present business model of selling personal information.
"There is a dilemma here unless Facebook is informing people about what access there will be to that personal information and enabling them to opt out. Explicitly opt out. In fact, they should be given the opportunity to decline to opt in. This kind of consumer right ought to be the subject of questioning before a congressional committee, likely the Commerce committee where I sit."