How to Get Started: Investigating Payment Gateways Online - bellingcat

This is the best summary I could come up with:

When investigating a website, app, or online shop, one of the key questions you may need to answer is ‘How are they making money?’

Furthermore, if the website or app is engaged in illicit transactions, tracing the payment gateway can help achieve accountability by identifying what sites they are using to earn money.

For example, for some of the AI deep fake services we investigated here we found that companies would accept different payment methods depending on how you tried to pay – via their website, via a web browser or via Telegram.

Sellers may want to direct their users away from their website to more private forums such as Telegram to facilitate transactions and avoid detection.

Clicking through to ‘Go To Payment’ gives us a new screen that lets the user pay via credit card (ie MasterCard, Visa), a US Bank account (ie Wells Fargo, USAA), or through Cash App.

Using Browser Developer tools and following these simple steps, we were able to learn that Nudify.VIP created a decoy website to which they were redirecting their credit card payments to make Stripe think they were processing sales for a company called “Aiphotos.art.”

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TLDR: browser developer consoles let you see the code that runs a website. Also some sellers redirect to other sites for payments.

Bit of a warning though: Stripe JS loads when the plugin is installed whether the site is configured to use it for checkout or not. Also redirecting to other sites for checkout is not in itself nefarious just that it does happen to be a technique to hide the sellers product from the payment gateway.