If you type "foo" in Firefox's address bar and press Ctrl-Enter, you get http://www.foo.com/. Shift-Enter gives you http://www.foo.net/, and Ctrl-Shift-Enter gives you http://www.foo.org/.
I'm sure there's someone in the world who wants those shortcuts.
But I have never needed them. I have, instead, about a zillion times been peacefully typing a Quick Search and pressed Shift-Enter by mistake, usually because my search string ends with a quoted string and I'm still holding Shift down.
Like all normal humans, I use "g" as my Google Quick Search. So I might, for instance, type
g autoerotic "hydraulic shovels"
...then press Shift-Enter by mistake, and thereby try to go to http://www.g autoerotic "hydraulic shovels".net/.
Is there something in about:config to disable these shortcuts? I can't find it.
UPDATE: As per Avery Morrow's comment below, this problem is indeed now fixable, with the updated version of his extension. Yippee!