Shellshock the bug could be bigger than Heartbleed.
The Bash vulnerability being referred to by some as ‘Shell Shock’ allows an attacker to run a wide range of malicious code remotely.
A vulnerability in Bash, the software used to control the command shell in many flavors of Unix, has been shown to be present in OS X.
But today Apple release a update for OS X 10.9/8/7.
Download the right version for your OS X.
Both versions of Yosemite include an update to Bash shell, versioned as 3.2.53(1), to address the Shellshock flaw.