On October 4th, in a security notice Canonical published details about DBus regressions affecting 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, DBus could be made to run programs as an administrator. An update, USN-1576-1 fixed vulnerabilities in Dbus but caused a regression for certain services launched from the activation helper, and caused an unclean shutdown on upgrade.
The security flaws can be fixed if you upgrade your system(s) to the latest dbus and libdbus packages, 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.
To update your system, please follow the instructions of the official wiki.