On October 4th, in a security notice Canonical published details about a few libxslt vulnerabilities for its Ubuntu 12.04 LTS, Ubuntu 11.10, Ubuntu 11.04, Ubuntu 10.04 LTS, and Ubuntu 8.04 LTS operating systems.
According to Canonical, applications using libxslt could have been made to crash or run programs as your login if they processed a specially crafted file.
A remote attacker could have obtained potentially sensitive information, cause libxslt to crash, possibly execute arbitrary code, or cause a denial of service.
The security flaws can be fixed if you upgrade your system(s) to the latest libxslt1.1 package, specific to each operating system. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A system restart won't be necessary to implement the changes.