1 - Go to page labs.adobe.com/downloads/flashplayer10_square.html and download plugin for 64-bit linux.
2 - Uncompress the file and save libflashplayer.so anywhere in the system
3 - Go to page www.google.com/chrome/ and donwload google-chrome installer 64-bit .deb installer for Ubuntu
4 - Run the command below. Somehow, the installer managed to find the libflashplayer.so file.
sudo dpkg -i google-chrome-stable_current_amd64.deb
5 - Say goodbye to firefox 64-bit.