"The editor consists of a small form with a textarea and a submit button (oh and besides, for a little feeling of fake security, there is a password box :) )."
To me this sounds like a bad idea. Are you saying that if someone should stumble upon this page you have setup they could edit files on your webserver via a browser without having to provide any type of valid username/password?
If so I would re think that before worrying about anything else.