The Apple OS X Bash Update 1.0 was released on Tuesday. The update fixes a security flaw called Shellshock. That vulnerability was located in the bash Unix shell.

The Bash 1.0 update fixes an issue that made it possible for a remote attacker to execute arbitrary shell commands from a remote location.

In Apple’s release notes for the Bash Update 1.0 release, the company writes, “an issue existed in Bash’s parsing of environment variables. This issue was addressed through improved environment variable parsing by better detecting the end of the function statement.”

Apple added a suggested change to the parser state and added new namespace for exported functions.

The update is available for OS X Mavericks, OS X Lion, OS X Mountain Lion, and OS X Lion Server.

The security update can be downloaded here: http://support.apple.com/kb/DL1769

Mac users should execute the code as soon as possible.