Weeks ago, the developers announced the (at that moment) upcoming EOL for Ubuntu 13.04, essentially, Ubuntu 13.04 stopping to receive support and, therefore, being recommended to be replaced with stable supported versions of Ubuntu.
Today, the developers confirmed that, starting with January 27 2014, Ubuntu 13.04 is no longer to receive updates and support, EOL coming nine months after Ubuntu 13.04's official release.
"This is a follow-up to the End of Life warning sent last month to confirm that as of today (Jan 27, 2014), Ubuntu 13.04 is no longer supported. No more package updates will be accepted to 13.04, and it will be archived to old-releases.ubuntu.com in the coming weeks."
As a consequence, the users are to upgrade to Ubuntu 13.10, in order to enjoy a secure, up-to-date and supported Ubuntu version, upgrade process step-by-step presented on https://help.ubuntu.com/community/SaucyUpgrades
