update bash to patch remote code exploitation

bash_update.sh

#!/bin/bash

# context: http://www.infoq.com/news/2014/09/bash-remote-exploit
# credit: http://stackoverflow.com/questions/16416195/how-do-i-upgrade-bash-in-mac-osx-mountain-lion-and-set-it-the-correct-path

brew upgrade && brew update
brew install bash

mv /bin/bash /bin/bash.old
ln -s /usr/local/bin/bash /bin/bash

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