Hasn't been working for a while. But still works on some earlier installs that I still have installed on the same machine, so I presume it is not an issue with XFCE 4.12 or Xorg 1:7.7+19 or Debian-stretch. If I double-left-click highlight a URL in, say, a txt document, then I can simply middle-click to paste that URL elsewhere, such as an xterm, or emacs window. This does not require Ctrl-C Ctrl-V. If I am running an older version of FF, say FF53, a middle-click paste anywhere in the browser window will get FF to load the URL in that window. But this no longer works in recent FF, such as FF62. To accomplish it requires first clearing the URL bar (double-left click to highlight, then backspace-key to delete) then re-highlighting the desired URL (double left-click), then middle-clicking in the empty URL bar. This pasting feature was working by default as recently as FF53, but it stopped working somewhere between 53 and 58. How can I get it working again?