14 DAY TRIAL // Canonical has published details in a security notice about a Unity exploit that has been corrected in Ubuntu 14.04 LTS (Trusty Tahr) operating systems.
The Ubuntu developers have said that a problem with the Unity lock screen could be bypassed in certain circumstances. Updating the system should solve this pesky issue.
According to the security notice, “It was discovered that in certain circumstances Unity failed to successfully grab the keyboard when switching to the lock screen. A local attacker could possibly use this issue to run commands, and unlock the current session.”
For a more detailed description of the problems, you can see Canonical's security notification. This is not a major vulnerability, but it needed to be closed nonetheless. In fact, this is not the first time that a user has found a way to circumvent the lock screen. This only happened after Ubuntu developers fashioned their own lock screen and they are still fixing various problems that pop up.
The flaw can be fixed if you upgrade your system(s) to the latest unity package. 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 (you will need to be root):
sudo apt-get dist-upgrade