Installation of flash player on Mozilla firefox in Ubuntu

Before you begin, first check whether Flash is already installed in your system. Visit below official Adobe flash tester page.

Test Your Flash Plugin (https://www.adobe.com/software/flash/about)

In this page, if you see a flash animation and a box mentioning “Version Information” of flash, then it is enabled in Mozilla in your system.

Alternatively, you can also visit about:plugins in Mozilla and check for flash plugin entry.

Now, let's update it as there are many vulnerabilities discovered in Adobe flash in the past year. Also, offline installation is also useful if you are
on internal network. Here  are the steps for manual installation:

1) Download the tar.gz archive from https://get.adobe.com/flashplayer
2) open it with the Archive Manager.
3) Unpack and copy libflashplayer.so to the plugins directory of Firefox -e /home/user/.mozilla/plugins
If it does not exist, create plugins directory and copy file -libflashplayer.so to it.

If "libflashplayer.so" exists in "/usr/lib/adobe-flashplugin/" directory, copy the latest "libflashplayer.so" file to this directory also as it is usually listed first in the path and is picked up by the browser.

And restart the firefox! That's it!