There is a simple keyboard shortcut, if you have copied formatted text and want to paste it into the ఫైర్ఫాక్స్ browser as unformatted text.
To paste the text as unformatted plain text into ఫైర్ఫాక్స్ బ్రౌజర్, press the following keys:
Ctrl + Shift + V
No extra plugins are required. This was tested in Firefox 52 on Windows 10. If this works in a different Firefox version or does not work in a specific Firefox version on various platforms let us and other users know in the comments section below.