We are currently having an issue with our checkout in Magento 2.1.5
If a user tries enough times, even though the order is "canceled", if there are enough rapid attempts, the order will go through and show as "Processing". However, there's no payment information. We are using Authorize.net only for transactions. We even get an email from Authorize.net stating the transaction is declined, but somehow it's making into Magento as a good order.
I don't think the problem is with Authorize.net as I can see the failed transactions and they're coming from a country where all transactions will be declined.
Does anyone know of a way to ban/block a user after "X" failed checkout attempts in Magento?