A crowd-sourced verification system used by Elon Musk’s X failed to flag a vast majority of false claims related to the U.S. midterm elections – including those promoted by the billionaire – a study said Wednesday.

Community Notes, which allows users to contribute notes that add context or corrections to posts, was introduced by X in late 2022 and the same model is increasingly being adopted by other tech platforms.

But researchers have repeatedly questioned its effectiveness in combating misinformation.

NewsGuard, a U.S. watchdog that rates the credibility of news and information sites, identified dozens of posts on X that advanced false claims related to the elections, including bogus allegations of election fraud.