For example, if you run a Stripe Connect platform, and you set up webhooks to receive some events asynchronously, Stripe will send you all events of the types you select about the accounts connected to your platform, no matter if the events are related to your platform or not.
There may be applications which might need to receive all the activity, but in a simple case of a marketplace which allows merchants to sell stuff and collect a small fee, this is a disturbing amount of information. If I were a bad actor, I could silently collect the information about my merchants' activity on the marketplaces of my competitors.
Moreover, if your platform has enough merchants, you could track their buyers. Stripe will readily hand over all this information to you. In a charge.succeeded webhook alone, you get quite enough information to fingerprint a customer, and if you use some deduction, you can identify them, too.
This sounds like putting a Ring of Power into the Gollum's hand all of a sudden.
I'm wondering if the marketplaces should hang a big warning, for privacy reasons, that "this site uses Stripe for payments. Any payment information might be shared with an unknown number of third parties, and there's diddly we can do about this."