I often sit at school with my laptop. If I walk away I normally lock the laptop, but when I forget to do so, a couple of people love to "prank" me with changing the image of my desktop, installing add-ons like the random John Cena thing, etc It was fun for the first time, maybe the second but it has gotten to the point that it's just annoying having to delete all the crap they might put on my laptop.
Is there an extension that prevents the adding extensions, edit bookmarks, etc. without entering a password or something? I already have Public Fox installed, but this just prevents people from getting into my add-ons page instead of also preventing people from adding additional crap to Firefox.