I have known this exploit for quite some time and they have yet to fix it. On the ssl.clickbank.net payment page, for example, You can see where I marked it red, after "&title" there is a number before it. If you edit that number to lets say 1, you will notice that the price has changed or is a different product. What is also bad about this is that if you have a test purchase set up, lets say its number 5, the customer can get to the test page and get your ebook/software for free. So all you clickbank publishers out there be careful, try not to have so many different prices.
yeah there's a much easier way to do this. Just change the original payment link e.g. http://1.<vendor>.pay.clickbank.net http://2.<vendor>.pay.clickbank.net http://3.<vendor>.pay.clickbank.net http://4.<vendor>.pay.clickbank.net I agree, you can find some interesting things this way such as test pages.
Ha!, right! I just tested out that, this is dangerous for publishers, but don't think many people know about this one so that's a positive thing. Well this is not good for us affiliates either .Tested a product that was selling for $29.99 and went to $17.77.