In a security notice, Canonical has published details about libxml2 vulnerabilities for its Ubuntu 13.04, Ubuntu 12.10, Ubuntu 12.04 LTS, and Ubuntu 10.04 LTS operating systems.
According to Canonical, several security issues were fixed in libxml2.
For example, it has been discovered that libxml2 would load XML external entities by default.
If a user or automated system were tricked into opening a specially crafted document, an attacker could have possibly obtained access to arbitrary files or cause resource consumption.
For a more detailed description of the security problems, you can visit Canonical's security notification.
The security flaws can be fixed if you upgrade your system(s) to the latest libxml2 package, specific to each distribution. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A system restart will not be needed to implement the changes.