Apple released security updates for Bash in OS X Mavericks, Mountain Lion, and Lion Monday afternoon to address the Shellshock flaw that became big news last week. Bash is a command line shell for OS X's UNIX underpinnings, and Shellshock could potentially give attackers an exploit to gain access to servers and user's computers.
Apple releases patch for Shellshock security flaw in Terminal's Bash shell
Shellshock went unnoticed for about 25 years even though it poses a serious security threat for UNIX and several versions of Linux that use the Bash shell. The flaw presents a security hole by letting commands stored in certain memory spaces to execute immediately.
Many companies that rely on UNIX and Linux responded quickly to release Shellshock patches, and now Apple has joined that list. The patch is important for average users even if they never launch the Terminal app because some apps and system services rely on Bash in the background.