Natours is a Tour Booking API. The attacker can easily take over any victim account by injecting an attacker-controlled server domain in the Host header when requesting the /forgetpassword endpoint. This vulnerability is fixed with commit 7401793a8d9ed0f0c250c4e0ee2815d685d7a70b.
The product contains a mechanism for users to recover or change their passwords without knowing the original password, but the mechanism is weak.