A critical vulnerability in client software used to interact with Git, a distributed revision control system for managing source code repositories, allows attackers to execute rogue commands on computers used by developers.The flaw affects the official Git client as well as third-party clients and software based on the original Git code. The issue only affects implementations running on Windows and Mac OS X, not Linux, because their file systems are case-insensitive -- NTFS and FAT for Windows and HFS+ for Mac OS X."An attacker can craft a malicious Git tree that will cause Git to overwrite its own .git\/config file when cloning or checking out a repository, leading to arbitrary command execution in the client machine," engineers from GitHub, a code repository hosting service, said in a blog post Thursday.The desktop and command-line implementations of GitHub's own client software for Windows and Mac are affected and have been updated.The Git development team released versions 126.96.36.199, 1.9.5, 2.0.5, 2.1.4, and 2.2.1 to address the flaw. Updates are also available for Git for Windows, also known as MSysGit, as well as the libgit2 and JGit libraries. Development software that use these libraries, such as Microsoft's Visual Studio, Apple's Xcode and Mercurial, have also been updated."We strongly encourage all users of GitHub and GitHub Enterprise to update their Git clients as soon as possible, and to be particularly careful when cloning or accessing Git repositories hosted on unsafe or untrusted hosts," the GitHub team said.The company scanned all repositories hosted on GitHub for trees that might attempt to exploit this flaw, but didn't find any. It also implemented protections that prevent such repositories from being created in the future.