You can quickly test your operating system to see if your bash version is vulnerable by following instructions on the Shellshocker website. TLDR, here is the command you need to run to test bash on your machine:
Note that the version of bash in my path (the newer one from MacPorts) is not affected by the vuln. Now I will test the version of bash installed as /bin/bash:
Notice that I piped the script directly to /bin/bash instead of relying upon the version of bash in my PATH. Because I have already installed Apple's update (noted below), /bin/bash is not affected either.