On December 3, Canonical published details about Firefox regressions for its Ubuntu 12.10, Ubuntu 12.04 LTS, Ubuntu 11.10, and Ubuntu 10.04 LTS operating systems.
According to Canonical, multiple regressions were introduced in the last Firefox update. A previous update fixed vulnerabilities in Firefox, but the new packages introduced regressions in cookies handling and the User Agent string. This update fixes the problem.
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.
Alternatively, you can download Mozilla Firefox 17.0.1
right now from Softpedia.