I build the checkout page that sends the customer to paypal. Everything works really fine.
But i notice that in the checkout page, the form have invisible fields, and in firefox with development tool i can activate the invisible fields and change their values.
Everything is in HTTP because i will not proccess the payment in the site, i will make everything in paypal.
For example, i am able to change the price from 78€ to 0.01€
Any one can say me how to prevent this issue?