Apple releases Bash update to plug Shellshock security flaw
On Monday, Apple released OS X bash update for Mavericks, Mountain Lion and Lion that addresses the recently discovered "Shellshock" security flaw that exploits the bash UNIX shell used by Apple computers.
The bug "Shellshock" is built into every version of bash since 1989. The potential risk is that a hacker could take control of your computer with the intent of gathering information and modifying the system files.
The update should appear in your Software Update or it can be downloaded directly from Apple.