Apple is aware of the recently discovered bash exploit nicknamed Shellshock, and is working quickly to provide a software update for OS X, the operating system that runs on the Mac.
The vast majority of OS X users are not at risk to recently reported bash vulnerabilities," an Apple spokesperson told iMore. "Bash, a UNIX command shell and language included in OS X, has a weakness that could allow unauthorized users to remotely gain control of vulnerable systems. With OS X, systems are safe by default and not exposed to remote exploits of bash unless users configure advanced UNIX services. We are working to quickly provide a software update for our advanced UNIX users.
The exploit reportedly affects most Linux- and Unix-based operating systems around the world, including OS X. That's millions and millions of computers and embedded devices, all of which will need to be updated as soon as possible.
If you're an advanced enough user to have enabled the types of services that can be exploited by Shellshock, you're also likely advanced enough to turn those services off for now, or to patch bash yourself using Xcode.
For everyone else, be informed but don't panic. Most people aren't aren't at high levels of risk. Stay informed, stay updated, but also understand that there's no real reason for significant concern at this point.