Robert Mueller. Alex Wong/Getty Images

This week saw a slew of critical revelations in the ongoing Russia investigation led by special counsel Robert Mueller; Facebook and its role in Russia's election interference; the explosive but unverified Steele dossier; and an elite Russian cybersecurity firm that's attracted scrutiny as Russia ramps up its aggression in the cyber space.

We got an important update from Sens. Richard Burr and Mark Warner, the chairman and vice chairman of the Senate Intelligence Committee, on the status of their investigation into Russia's interference in the election.

"The issue of collusion" between President Donald Trump's campaign and Moscow "is still open," Burr told reporters during a press conference.

New details also emerged about Russia's extensive use of Facebook to sow discord and spread misinformation during the election. A Columbia University social media analyst published research on the topic and found that Russian propaganda may have been shared billions of times on Facebook.

The company still doesn't know the full extent of Russian ads that were purchased because of the platform's self-service tool, and Axios reported Saturday that Facebook will now require targeted and politically tilted ads to be manually reviewed before they're approved.

Here's more on what you may have missed: