CVE-2026-53637: Sylius: Cart FormComponent allows modification or deletion of an already-completed order

A user opens the cart page in the browser. In the background, the order gets completed, e.g. an admin changes the status, or the user finalizes payment in another tab. The browser still displays the old cart: the LiveComponent is unaware the underlying order state has changed.

If the user then:

• clears the cart → clearCart() calls manager->remove() on the completed order: the order is permanently deleted from the database;
• removes a product → removeItem() mutates an item on the completed order;
• changes quantity → saveCart() overwrites data on the completed order.

In all cases, the customer’s order data is irreversibly corrupted or lost, even though the order has already been placed and paid for. The same vector can be triggered deliberately by an authenticated customer (keep the cart page open, complete checkout in another tab, then modify the “cart” to add quantity beyond what was paid for).