I mean, there are some developer/other tools that let change variables in Javascript enviroment and so on. Consider I have an AJAX request. So could user, for instance, manipulate variables I send with AJAX request so that they see something they are not used to see? Or, for instance, manipulate value of <select> so that it is other, not like in options given. I hope you understand what I mean.
But how to implement AJAX in this case? Can client create his own request? So just send error back if request was not like it should be?
YES!
You can’t rely on client side scripting for security!
Check out:
After your edit:
Yes.
Yes.