Comment by dghlsakjg

Guessing credit card numbers for the purpose of spending money that isn’t yours is openly malicious and illegal. I would also argue that credit card numbers are designed to restrict access. The company that issues them specifically says not to share the number and uses knowledge of that number to gate access to the spending function.

Sending get requests and having a server respond with a document is just how the internet works. If - big if - that is what happened, then someone is going to have to explain why those supposedly private documents were available to anyone who asked using a protocol designed to distribute documents publicly. Enumerating urls isn’t typically regarded as outright illegal.