trooper,
I almost see your point, but I'm not quite getting it...
I'm going to make an assumption: we don't trust ANY variable that is submitted, and check each variable for fitness for use. (well, maybe that's a big assumption...)
If that's the case, then letting the hacker see the variable only confirms what we have already assumed: the variable could have evil content.
Therefore it seems to me that it's an unavoidable risk that is not exacerbated by the form.
Am I just missing something?
'course, if someone has something like <a href="template.php?id=123"> and doesn't want everybody to see be able to see template.php?id=124, then I see your point. Is this what spoofing is?
thanks