URLs are leaked to third party if they contain typos
Open a new tab in the Tor Browser and type "https;//www.wikipedia.org" into the URL field (note the typo - a semicolon instead of a colon)
The Tor Browser jumps to startpage.com and searches it for "https;//www.wikipedia.org"
Users may make typos - and I think there is no need to leak URLs with typos to a third party (startpage). You should patch Firefox so that anything typed into the URL field is never sent to a third party.
There is already a special field for startpage search in the navigation toolbar - so there is no need to use the URL field for searches.
Trac:
Username: torar