On September 24, 2014 a vulnerability called "Shell Shock" or "Bash Bug" was discovered in the widely used Bash software (versions 4.3 and earlier), which impacts Linux and Unix based operating systems, including Mac OS X.
None, but this will affect public-facing Web Servers that have not yet been patched.
Bash vulnerability, dubbed “Shell Shock,” allows attackers to take complete control of a targeted Linux- or Unix-based system. It is recommend that all users of these systems implement the available patches immediately. To date, the following vendors have published information, including patch details: