Politico reports today that according to a knowledgeable source, Facebook knows that “shadowy Russian buyers” purchased advertisements on its platform that aimed to influence the 2016 presidential race. The ads, we learn, praised Donald Trump, Green Party candidate Jill Stein, and Hillary Clinton’s Democratic primary rival Bernie Sanders — even after he dropped out of the race. Although many of the ads said nothing about Clinton, they all either boosted a Clinton rival, or were otherwise aimed at sowing divisions on issues prevalent in the campaign.

The Politico scoop is just the latest tidbit of information we have learned about Facebook’s role in disseminating Russian-backed propaganda aimed at disrupting the 2016 presidential campaign, following its belated disclosure earlier this month that Russian entities had indeed used fake accounts to buy political ads.

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That’s obviously critical to Mueller’s investigation. But it is also information that the American public deserves. As Nate Persily, a Stanford professor and election law expert, argues: “It doesn’t seem to be a terribly chilling idea to say that we should be able to know how much money is being spent on election-related advertisements online, and we ought to be able to see what those advertisements were and who they were targeted to.”