With JavaScript, it is quite easy to have an <input> element automatically take on a value once the page has loaded, so long as its type attribute is not ‘file’; this makes perfect sense, of course, given that auto-submitting a form containing sensitive data to a server is a single line of code away.
However, on a home server (WAMP, if it’s at all helpful), this threat is eradicated entirely. So, is there by chance a way to bypass a file input field’s default behavior in a situation where the risk is effectively zero?
iMacros for Firefox lets you set up little ‘browser automation’ scripts that might do what you want.