> Unfortunately, all major browsers now use a combined address and search bar. So, if you’re typing in the address of a sensitive website to go directly there, your keystrokes as you type will be sent to your default search engine and your search engine may be able to determine the website address you’re typing in manually.

That's why it's a good idea to split the search box in the Firefox settings. Ctrl-l takes you to the address bar which doesn't load any remote data, and ctrl-k takes you to the search box on the right, which does send keystrokes to the search engine.

Settings → Search → Add search bar in toolbar (check that box)

Also uncheck "Show search suggestions in address bar results"

Problem solved, for now.