https://www.bleepingcomputer.com/news/apple/apple-to-fix-bug-that-bypasses-communication-controls-for-kids/

Apple rolled out the Communication Limits feature in iOS 13.3 on Tuesday with a bug that allows kids to bypass parental controls that prevent them from talking to anyone that is not in the contacts list.

The miss on Apple's part allows children with an iPhone or an iPad configured with Communication Limits to add a new number to the address book in order to bypass the restriction imposed by the feature.