The Contact Form 7 WordPress plugin before 2.5 does not validate the host of a user-supplied return URL before using it as the success and cancel redirect targets of a Stripe checkout, allowing an unauthenticated attacker to redirect a victim, via a crafted link, to an arbitrary external site after the checkout flow.
https://wpscan.com/vulnerability/b53cc13d-c59e-4c11-aa71-fa1c38c2a34d/