In Opera I was able to add an item to the context menu which was bound to a script on my filesystem. So, for example, when I right-clicked an image and clicked on this menu-item, the URL was passed to this local script as an argument.
Is there any way to do this with FireFox (even if it's not context-sensitive, i.e. just pass the current page's URL)?
There used to be an extension to do this called ContextMenu Extensions but it's over a decade old and Firefox version 0.5 :)