The Mailchimp for WooCommerce WordPress plugin before 6.3 does not require authentication or verify ownership before loading a saved cart from a request-supplied identifier that is derived from a customer's email address, allowing an unauthenticated attacker who knows a customer's email address to confirm that the customer shops at the store and to read that customer's saved cart contents.
https://wpscan.com/vulnerability/f4d7b94a-7699-464c-a646-5946837b363a/