Upsell Funnel Builder for WooCommerce <= 3.0.0 - Unauthenticated Order Manipulation

The Upsell Funnel Builder for WooCommerce plugin for WordPress is vulnerable to order manipulation in all versions up to, and including, 3.0.0. This is due to the plugin allowing the additional product ID and discount field to be manipulated prior to processing via the 'add_offer_in_cart' function. This makes it possible for unauthenticated attackers to arbitrarily update the product associated with any order bump, and arbitrarily update the discount applied to any order bump item, when adding it to the cart.