Google Chrome browser’s built-in auto-updated adobe flash is more recent than can be downloaded individually due to the partnership between Google and Adobe. If you prefer Ubuntu default Firefox web browser, it is easy to use the Chrome browser’s built-in flash in Firefox although it requires Google Chrome installed. Just go to www.google.com/chrome and download the deb.
Once installed open a terminal from Applications -> Accessories -> Terminal, and navigate to :
Link the flash player from Chrome to Firefox with the command:
sudo ln -s /opt/google/chrome/libgcflashplayer.so ./
Finally, disable Firefox’s previous flash plugin from Firefox -> Tools -> Add-ons -> Plugins tab
Now, keep your system updating with Update Manager and you always have the latest patched adobe flash in Firefox.
Read original tutorial from OMGUbuntu