The WordPress Simple Shopping Cart plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 5.1.3 due to lack of randomization of a user controlled key. This makes it possible for unauthenticated attackers to access customer shopping carts and edit product links, add or delete products, and discover coupon codes.
https://www.tipsandtricks-hq.com/ecommerce/wp-shopping-cart
https://plugins.trac.wordpress.org/changeset/3284572/
https://developer.wordpress.org/reference/functions/wp_generate_password/