how should a web application verify a redirect comes from a trustworthy source?

how should a web application verify a redirect comes from a trustworthy source?

This document has a sequence diagram (annotated and shown below) explaining how Stripe handle's a Checkout Session.

My question : When a customer is returned to the successUrl = www.example.com/some/specific/path, how can www.example.com (either client or server) verify it is truly coming from stripe.com instead of a malicious user?

Please see the sequence diagram below more details.