Mike Isaac and Sheera Frenkel

The Facebook and Instagram owner said it would bar Russian media outlets including RT, which the U.S. has accused of acting as an intelligence arm.

The criminal charges against Pavel Durov, Telegram’s founder, raised concerns in Silicon Valley about encryption and the app’s approach to privacy and security.

In four new studies, researchers found complicated results from experiments on Facebook’s and Instagram’s algorithms, suggesting there was no silver bullet to fixing the platforms.

In an internal meeting this week, Mr. Zuckerberg said the tech giant was facing one of the “worst downturns that we’ve seen in recent history.”

In an internal meeting this week, Mr. Zuckerberg said the tech giant was facing one of the “worst downturns that we’ve seen in recent history.”