14 DAY TRIAL // Canonical has revealed that a vulnerability that affected the Unity Settings Daemon Daemon has been closed in Ubuntu 15.04 and Ubuntu 14.04 LTS by the developers.
Unity Settings is not the kind of component that gets updates with vulnerability issues, but this is something developed by Canonical for Ubuntu. It's not a package from upstream and it's a good idea to upgrade as soon as possible.
"It was discovered that the Unity Settings Daemon incorrectly allowed removable media to be mounted when the screen is locked. If a vulnerability were discovered in some other desktop component, such as an image library, a local attacker could possibly use this issue to gain access to the session," said the developers.
For a more detailed description of the issues, you can see Canonical's security notification. Users should upgrade their Ubuntu distribution in order to correct this issue. The vulnerability can be fixed if you upgrade your system(s) to the latest package specific to each distribution. To apply the patch, users can simply run the Update Manager application.
If you don't want to use the Software Updater, you can open a terminal and enter the following commands (root is needed for this to work):
sudo apt-get dist-upgrade