This is a message from a fraud detection system Google uses to prevent malicious payment transactions from been executed. Before executing a payment transaction, Google tried to analyze how safe a transaction is. Multiple parameters can impact this check. A probability of "bad transaction" rises, for instance, when multiple payments are executed by different devices using the same credit card very often, or when same credit card is used by multiple accounts, or when user pays and then cancels payments multiple times in a row, etc.
It will usually go away after some time. If you have any issues with it you will have to contact Google Play Support or you can refer to this article if you want to know a basic run down on how to properly contact Play Store Support; Contact Play Store Support.