Facebook’s Messenger Kids is supposed to provide parents complete control over who their children chat can with on the app. But as The Verge reported on Monday, that key promise appears to have been broken, thanks to a design flaw with the app.

According to the report, Messenger Kids had a design flaw that allows for a situation in which a child can enter a group chat with other users — including adults — who hadn’t been preapproved by their parents.

A Facebook spokesperson confirmed with Business Insider on Monday that children had been allowed to chat with friends-of-friends in group settings within Messenger. All users in the chat groups had been approved by someone’s parents, the spokesperson said, just not necessarily approved by the parent’s of the child entering the chat.

“We recently notified some parents of Messenger Kids account users about a technical error that we detected affecting a small number of group chats,” Facebook told Business Insider. “We turned off the affected chats and provided parents with additional resources on Messenger Kids and online safety.”

The Facebook spokesperson would not give an exact number of children impacted, except to say it was somewhere in the thousands. The spokesperson also said the bug was discovered over the last couple weeks, and since then, the company has notified the parents of affected children.

Privacy settings for children having one-on-one chat conversations within Messenger Kids were not affected, according to Facebook.