Tip: If your #firefox keyword search has been messing up recently, including your trigger keyword (eg. my `wp` for Wikipedia) in what's searched for or copy-pasting the search you just did instead of the retrieved URL, try toggling Settings > Search > Show search terms in the address bar on results pages.

If you're running into the same thing as me, the bug is a new feature that leaves the state of the address bar un-reset after you press Enter.