Se você quiser atualizar suas versões do Firefox fora dos pacotes do Ubuntu, sugiro que use ubuntuzilla . Ele funcionará não apenas para esta versão, mas também obterá atualizações futuras para você.
The Ubuntuzilla project is a python script that allows the user to install the latest versions of Mozilla Firefox, Mozilla SeaMonkey, and Mozilla Thunderbird on Ubuntu Linux. It also works on other Linux distributions that are derivatives of Ubuntu.
Aqui está uma lista selecionada de recursos, na página do projeto ubuntuzilla:
* Automatically detects and downloads the newest Firefox, Thunderbird, SeaMonkey release from the Mozilla servers
* Allows you to make a choice of language for Firefox or Thunderbird
* Verifies the GPG signature (assures package integrity against malicious tampering or corrupt download) for Firefox or Thunderbird
* Verifies the MD5 sum for SeaMonkey
* Makes a date-stamped back-up of your Firefox, Thunderbird, SeaMonkey profile data
* Automatically integrates Firefox plugins that you have installed from the Ubuntu repositories
* Installs the new Firefox in /opt/firefox, Thunderbird in /opt/thunderbird, SeaMonkey in /opt/seamonkey
* Creates a SeaMonkey menu item in Applications -> Internet menu
* Checks all steps for successful execution
* Has a 'remove' action to remove the official Mozilla build and restore system to pre-installation state.
* Installs an update checker job that periodically performs automatic checks for new versions of Firefox, Thunderbird, or Seamonkey.
* Automatically checks for the latest Ubuntuzilla release and updates itself, to keep up with possible changes in the Mozilla website and release servers.
* Comes conveniently packaged in a .deb for easy installation
* Includes a very helpful man page, for those who don't like to read websites.
Eu mudei para usar o ubuntuzilla há um ano, e não sinto a necessidade de reverter desde então. Sua melhor característica é que ele permite que você instale sem problemas versões beta, fornecendo manualmente a versão para a qual deseja atualizar.