On February 19, Canonical published details about Firefox vulnerabilities for its Ubuntu 12.10, Ubuntu 12.04 LTS, Ubuntu 11.10, and Ubuntu 10.04 LTS operating systems.
According to Canonical, Firefox could be made to crash or run programs as you login if it opened a malicious website.
For example, multiple memory safety issues affecting Firefox were identified. If the user were tricked into opening a specially crafted page, an attacker could possibly exploit these to cause a denial of service via application crash.
For a more detailed description of the security problems, you can visit Canonical's security notification
Users can simply fix the security flaws by upgrading their operating systems to the latest Firefox package, specific to each distribution.
A normal system update, executed with the Update Manager, will implement all the necessary changes. A complete system restart is not necessary, but you will have to restart the application.
Alternatively, you can download Mozilla Firefox 19.0
right now from Softpedia.