Imagine situation like this:
You top-up £10 revolut via 3rd party card (i.e by Monzo card). After 2 minutes you top up £10 your 3rd party card (i.e Monzo card) by using Revolut card. You do it many times. And every users does that. AFAIK top-ups by card cost Revolut some fee to card processors etc and that scenario can make Revolut (and 3rd party) loss a lot of money. Is Revolut secured against this scenario by, for example, daily limit of top-ups? This could be done as “hackers” attack to make revolut bankrupt.