Recently, I've been seeing Firefox present me a bar asking "Refresh the page for the changes to take effect", and giving me the option to refresh now or later, and no close icons. Like this:
It basically appears at a yet unknown interval, and I still haven't found if it comes from Firefox itself, or from some extension. I've checked all my active extensions' options and none of them seem to be related to this behaviour.
Can someone please point me in the right direction?