The leading social network said it has been shutting down the group chats involved and notifying thousands of parents that their children many have unintentionally connected with strangers.
"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 said in response to an AFP inquiry.
"We turned off the affected chats and provided parents with additional resources on Messenger Kids and online safety."
Technology news website The Verge first reported on the development, publishing a copy of an alert informing parents that the flaw allowed a child's friend to create a group chat involving people who were not on their child's list of approved connections.
Group chat involvement was still limited by restrictions set by the parents of whoever got it going.
Facebook in December 2017 introduced a version of its Messenger application designed to let children between six and 12 years old connect with others under parental supervision. No in-app purchases are allowed.
The social media giant said at the time that it created the app as a safe environment because many children had been going online without safeguards.
Facebook's rules require that children be at least 13 to create an account.
The slip comes as Facebook works to rebuild the trust of users and regulators, and could prompt scrutiny as to whether the leading social network violated law regarding the privacy of children.
It also comes as the California-based internet giant continues to deal with the aftermath of revelations that personal data on tens of millions of users was hijacked by the political consultancy Cambridge Analytica, which was working on the Donald Trump campaign in 2016. — AFP