Hello Linux Geeksters. Recently, both Firefox 27.0.1 and Thunderbird 24.3.0 (the latest stable versions available, for now) have been added to the default repositories of Ubuntu 13.10, Ubuntu 12.10 and Ubuntu 12.04.
So, in order to get the latest versions available of Firefox and Thunderbird, on Ubuntu 13.10 Saucy Salamander, Ubuntu 12.10 Quantal Quetzal, Ubuntu 12.04 Precise Pangolin and derivative systems like: Linux Mint 16 Petra, Linux Mint 14 Nadia, Linux Mint 13 Maya and Elementary OS 0.2 Luna, you can either:
Update the local repository index and install the firefox and thunderbird packages:
$ sudo apt-get update
$ sudo apt-get install firefox thunderbird
Or perform a system upgrade:
$ sudo apt-get update
$ sudo apt-get dist-upgrade