Just update the system in order to fix the problem
On November 21, Canonical published details about UnityWebapps vulnerabilities for its Ubuntu 12.10 (Quantal Quetzal) operating system.According to Canonical, the UnityWebapps library could have been made to crash or to run programs as users log in, if it opened a malicious website.
It was discovered that libunity-webapps improperly handled certain hash tables. A remote attacker could use this problem to cause the UnityWebapps library to crash, or possibly to execute arbitrary code.
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 the operating systems to the latest libunity-webapps0, 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.