Is the salary earned from working in credit card programming considered unlawful, especially given the possibility of these cards being used in illicit ways, and knowing that the worker is compelled to this job due to the unavailability of an alternative?

It is not permissible to work in the field of systems related to international credit cards, and the salary derived from it is unlawful (haram); because these cards are based on usurious transactions, and working in them constitutes assisting in sin. This is unless you are compelled to remain in it, to the extent that you cannot find what suffices your needs and the needs of those you support. In such a case, it is permissible for you to remain until the necessity ceases.