This sandbox is dedicated for showing how you can modify PayU payment form parameters without knowing private key. Read more about how you can buy 10x more for the same price here.
To test it out, firstly try to submit below form. It looks pretty obvious, total amount is result of multiplication of quantity and unit price.
But now consider next form, parameters are slightly different (we moved “9” from price to quantity), total amount remained the same and so signature. Come on, give it a run and check if PayU complies!
How is this even possible? Read full article here.