In order to solve this issue you will have to update the operating system
On February 18, Canonical published details about a Boost vulnerability for its Ubuntu 12.10 (Quantal Quetzal) operating system in a security notice.According to Canonical, gBoost incorrectly validated certain UTF-8 sequences.
It was discovered that the Boost.Locale library incorrectly validated some invalid UTF-8 sequences. An attacker could possibly use this issue to bypass input validation in certain applications.
The security flaws can be fixed if you upgrade your system(s) to the latest gnome-screensaver package for Ubuntu 12.10 (Quantal Quetzal) the operating system. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A normal system update, executed with the Update Manager, will implement all the necessary changes. A complete system restart is not necessary.
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.