By default, Firefox is set to automatically update itself but you can always do a manual update. Here's how:
Note: If you use your Linux distribution's packaged version of Firefox, you will need to wait for an updated package to be released to its package repository. This article only applies if you installed Firefox manually (without using your distribution's package manager).
Click the menu button
, click help
and select About Firefox.On the menu bar click the Firefox menu and select About Firefox.
The About Firefox window will open and Firefox will begin checking for updates and downloading them automatically.
When the updates are ready to be installed, click Restart Firefox to Update.