The Payment Button for PayPal WordPress plugin through 1.2.3.44 does not enforce the merchant-configured price server-side and trusts a client-supplied payment amount, allowing unauthenticated attackers to create a real PayPal order against the merchant for an arbitrary lower amount.
https://wpscan.com/vulnerability/97c08603-c407-43b2-ab2c-e39f85e89ebe/