YouTube star James Stephen Donaldson, better known as Mr. Beast, has acquired youth-focused financial services app Step.

Opening statements began in a trial claiming social media companies design addictive products that cause personal injury.

The lawsuit in question involves Christopher Cordova, who runs the Denver Metro Audits channel, and Jonathan Huneault, creator of the Frauditor Troll channel.

A closely watched test case could rewrite the rules of engagement for social companies and their youngest users — and leave tech titans on the hook for billions in damages.