While I was on holiday in Andalucia (Olé!) a vulnerability was found for the Bash shell, called Shellshock (or BashDoor).
So you’ll be wanting to secure yourself up then. First up, lets see if you are vulnerable:

env x='() { :;}; echo vulnerable' bash -c "echo this is a test"

If the output contains ‘vulnerable’, then you need to fix it. If not, you’re all good. To fix it:

sudo apt-get update
sudo apt-get -s upgrade
sudo apt-get  upgrade

Now get back on with your work! 😉