With current git HEAD (b961235b197647d6649ef3d48d7cc2cecafe3d47), instead of opening a URL properly, xdg-open attempts to open two tabs, the first navigated to "http" and the second to the rest of the URL.
I've tracked this down to a missing "unset IFS" after "for browser in $BROWSER; do", leaving IFS=":" around to mess with eval.
I believe this is the same issue I also reported. Apparently I didn't find this report before I submitted mine. Sorry for that.
*** This bug has been marked as a duplicate of bug 45859 ***