After update to newest Firefox version on Fedora 25 my gnome shell integration stopped working. When visiting website I was greeted with following message:

To control GNOME Shell extensions using this site you must install GNOME Shell integration that consists of two parts: browser extension and native host messaging application.

When I followed the link and installed gnome shell integration Firefox plugin I was getting following error:

Attempt to postMessage on disconnected port

Turns out issue is with Firefox disabling NPAPI extensions in latest Firefox 52 release, so you’ll left with Chrome’s WebExtensions. To tie Gnome and Firefox together in that “new way” you’ll need to enable Chrome Gnome shell integration. To do that you can use following commands:

sudo dnf copr enable region51/chrome-gnome-shell
sudo dnf install chrome-gnome-shell

Refresh the site and you should be able to install extensions normally once again.