I've faced it a long ago but it is still so and is very annoying. Every time when I load a temporary extension file on addon debugging page (about:debugging#addons), Firefox leaves two handles opened (file handle and mapping handle), so I can't modify extension and click Reload button (Windows doesn't allow modifying of locked file). I have to rename extension file, copy with original name, modify, reload and remove renamed file in order to modify and reload extension w/o restarting Firefox. I believe Firefox shouldn't behave as it does, it should close handles after loading extension (or maybe copy extension to a temporary location if it really requires this mapping opened). So is there a work-around for such Firefox behaviour? Or how can I report this as a bug? (I've tried to register on bugzilla.mozilla.org but it prohibits new registrations.)