SDCM times mall any item 0 yuan purchase

You can purchase any item at any amount in the SDCM era Mall.
1. First, go to the mall, purchase any product, and capture the package when submitting the product quantity. You can change the number of items to a negative value. successfully submitted: 2. The order cannot be settled because the total number of items is 0 or negative. In this way, we can buy a few more products, some of which are changed to negative numbers, and some of which are changed to positive numbers. The total number of products is positive. 3. Then we settle the order. 4. After filling in the order, we can submit the order successfully: 5. Finally, let's make the payment. Click "Pay now" to see if we only pay the amount in our order. 6. Okay. From the amount already paid by the order number, we can see that we only pay 12 members. In this way, we purchased nine items totaling 2412 yuan for 12 yuan.
 Solution:

Do not filter illegal data on the foreground. Determine and submit valid data at the backend.