In PrestaShop before version 1.7.6.4, when a customer edits their address, they can freely change the id_address in the form, and thus steal someone else's address. It is the same with CustomerForm, you are able to change the id_customer and change all information of all accounts. The problem is patched in version 1.7.6.4.
In PrestaShop before 1.7.6.0 RC2, the id_address_delivery and id_address_invoice parameters are affected by an Insecure Direct Object Reference vulnerability due to a guessable value sent to the web application during checkout. An attacker could leak personal customer information. This is PrestaShop bug #14444.