You probably heard it a million times. It is one of the golden rules of web-development. Do not rely solely on client-side validation to ensure you get the data that you expect from the browser. Anyone can send you a crafted request that bypasses your script validation. Always validate on the server as well. And yet, I see a lot of commercial sites that ignore this rule, and it is easy as hell to break their logic. In fact, with the following simple steps I will show, you can bypass any javascript...