Adobe Flashplayer on Firefox -
How to install Adobe FlashPlayer on Firefox
Determine install location of Firefox. If installed from source, its wherever the Firefox folder is. General practice dictates that it should probably be in /usr/local/ so let's assume that its there for now.
Download "Other Linux" flash player from adobe.
tar -xvf install_flash_player_xx_linux.xxx.tar.gz
Make libflashplayer.so executable (chmod a+x) I'm not sure if this is needed, but I did it anyway.
Move libflashplayer.so to /usr/local/firefox/browser/plugins. If the plugins directory isn't present, create it.
Restart / Open Firefox.
Enjoy botnet free browsing with Firefox and still enjoy sites like Twitch and Vimeo.