https://www.cnet.com/news/googles-data-gathering-app-may-have-also-violated-apples-policies/

Earlier this week, Facebook landed in hot water for a similar app that gave users between the ages of 13 and 35 a payment of $20 a month plus referral fees for their phone and web activity. Facebook could access the data after users installed a "Facebook Research" VPN app. 

Apple said in a statement that Facebook's app violated its policies by using its membership in Apple's Enterprise Developer Program "to distribute a data-collecting app to consumers, which is a clear breach of their agreement with Apple." The iPhone maker added that it would revoke enterprise certificates from developers who use that certificate to distribute apps to consumers.