This is a regression, the range is 2016-10-31 to 2016-11-01. Mozregression-gui is unable to bisect further.
Drag any link/url to the address bar (or, in an opened page, drag the page's URL into itself)
A "ghost" caret appears at the beginning of the address bar. Typing anything (while the address bar is not focused, of course) does nothing
I can reproduce the issue on Nightly67.0a1 Windows10 en-US build too.
Regressed by: 74b268465bc7 Marco Bonardo — Bug 1310737 - Urlbar doesn't properly handle %S and POST keywords. r=adw