Ask HN: How did Favor get my new credit card #

As others have stated, they use Stripe for payment processing.

Not sure the exact mechanics behind it, but essentially the banks send out updates to credit cards to processors. Processors like Stripe then automatically update those details within their systems.

https://support.stripe.com/questions/how-can-i-keep-customer...

huh, not sure i like this, so if i give someone my cared they have my account number forever? while its a pain to re-enter data, it was sort of nice to start with a clean slate...

Stripe has a feature that does this