Lenin is sometimes said to have predicted that capitalists would sell Russia the rope with which they would be hanged. Yet not even Lenin could have imagined Vladimir Putin’s success in getting some of the largest Western companies to subsidize his disinformation efforts by advertising on his government-run “news” websites.

The top programmatic advertiser on Mr. Putin’s Sputnik News site? The Oracle of Omaha, Warren Buffett, through ads bought on behalf of Berkshire Hathaway’s Geico insurance. Sputnik News peddles Kremlin propaganda on topics such as Syria and straightfacedly reports Mr. Putin’s denials of interfering in other countries’ elections.

Geico is hardly alone in financing propaganda through what’s called “programmatic advertising,” ads that are placed automatically by algorithms, without judgment based on the content or journalistic standards of the websites. Mr. Putin’s leading disinformation arm, RT.com, attracted programmatic advertising from 477 companies and brands over a recent six-month period, according to data collected by Moat, an advertising technology service. Among RT.com’s top 20 programmatic advertisers: Amazon, PayPal, Walmart and Kroger. For Sputnik, its 196 programmatic advertisers in addition to Geico included Best Buy, ETrade and Progressive Insurance.

These all-American brands don’t intend to subsidize the Kremlin. The problem is that with programmatic advertising brands can target the kinds of audiences they want to reach online, rather than specifying, as they once did, on which websites their ads should appear. As a result, these ads inadvertently end up on all kinds of inappropriate sites.