Canonical usually updates their repositories with the latest version of Firefox for all supported operating systems, but the latest Firefox 24.0 arrived with a two-day delay for Ubuntu 13.10 (Saucy Salamander).
In all fairness, Ubuntu 13.10 hasn't been released yet, but Canonical has a habit of implementing the latest versions as soon as possible. That's also true for the Linux kernel, which has been updated to the latest stable version.
The latest update to Firefox has been accompanied by a lot of repaired vulnerabilities, that exposed the application that crashes and other problems.
The update process for Mozilla Firefox 24.0 is very simple. Just update the operating system and the update will be installed.
You will have to restart the Internet browser in order to use the new version. Alternatively, you can also download Firefox 24.0 from Softpedia.