What is the ruling on advertising for online stores that only accept payment via usurious credit cards, by placing links to these stores on a website or web directory?

Consider the ruling regarding stores that stipulate payment by credit cards. If their dealings are permissible, then there is no harm in advertising and promoting them. However, if they stipulate that the card must exclusively be from an interest-based (usurious) bank, then it is forbidden to cooperate with them. As for the mere fact that they do not accept cash manually but rather through a credit card from any source, this does not prevent dealing with them, because some credit cards are permissible. The ruling on dealing with these stores depends on the permissibility of their transactions, their field of work, and their merchandise.