“We have a responsibility to protect your data, and if we can’t then we don’t deserve to serve you,” Mr. Zuckerberg wrote. “I’ve been working to understand exactly what happened and how to make sure this doesn’t happen again.”

Here are the steps the company is taking to address the issue:

• “We will investigate all apps that had access to large amounts of information before we changed our platform to dramatically reduce data access in 2014, and we will conduct a full audit of any app with suspicious activity.”

• “We will restrict developers’ data access even further to prevent other kinds of abuse.”

• “We want to make sure you understand which apps you’ve allowed to access your data. In the next month, we will show everyone a tool at the top of your News Feed with the apps you’ve used and an easy way to revoke those apps’ permissions to your data.”

Mr. Zuckerberg had drawn criticism for his response to how Cambridge Analytica improperly obtained data on 50 million Facebook users. In the days since the news first broke this weekend, he had not commented publicly on the crisis.

That contrasts with how other tech chief executives have addressed crises at their firms.

Kevin Roose and Sheera Frenkel of the NYT report:

When a former engineer revealed a pattern of sexual harassment at Uber last year, Travis Kalanick, then the company’s chief executive, said he would immediately open an investigation. When users complained about bugs and problems with the Apple Maps app in 2012, Tim Cook, the company’s chief executive, released a statement that said “we fell short.” And in 2011, when Netflix tried to split off its mail-order DVD business into a company called Qwikster, its chief executive, Reed Hastings, wrote a letter to the public. “I messed up,” he said. “I owe everyone an explanation.”

So why did it take so long for Mr. Zuckerberg to respond? Kate Losse, an early Facebook employee and Mr. Zuckerberg’s former speechwriter, told the NYT: “My guess is that what is giving Zuckerberg pause at this point is the question of how to acknowledge and explain this state of affairs while at the same time mitigating the concerns that will come from people finally understanding how this all worked.”

