Linux Kernel privilege escalation
The most interesting security story last week was probably a new kernel privilege escalation flaw. If you simply run something like a single user desktop machine, flaws such as this aren't all that serious, as it's unlikely there are any untrusted users on your system.
Things like servers pose a much greater risk where it's likely you have untrusted users able to execute arbitrary code on the machine in question. A flaw such as this would allow such a user to run commands as root. If this is your setup, there is a possible mitigation.