In the event that you discover your Mac is vulnerable to Shellshock, the following action should be taken.
- http://support.apple.com/kb/DL1769 – Mavericks (10.9.5 and above)
- http://support.apple.com/kb/DL1768 – Mountain Lion (10.8.5)
- http://support.apple.com/kb/DL1767 – Lion & Lion Server (10.7.5)
To check whether you are vulnerable see Identifying Shellshock for full details on how to identify it.