FluentCart < 1.4.0 - Subscriber+ Subscription Payment-Method Tampering via IDOR

The FluentCart A New Era of eCommerce WordPress plugin before 1.4.0 does not verify that a subscription belongs to the requesting customer in several of its payment-method endpoints, allowing any authenticated customer to act on another customer's subscription (changing its payment method, or cancelling and re-binding it) when they know the target subscription identifier.