The OS X command line developer tools include an old version of the Git source code management system that exposes Mac users to remote code execution attacks.
The Git client allows developers to interact with source code repositories. It is not installed by default on Mac OS X, but it is included in the Command Line Tools package for Xcode, Apple's integrated development environment (IDE).
Software developers who create applications for OS X or iOS are likely to use Xcode and to have Apple's Command Line Tools package installed on their Macs. The latest version of this package includes Git version 2.6.4, released in December.