Affected: git-lfs

On Windows, if Git LFS operates on a malicious repository with a `..exe` file as well as a file named `git.exe`, and `git.exe` is not found in `PATH`, the `..exe` program will be executed, permitting the attacker to execute arbitrary code. This does not affect Unix systems. Similarly, if the malicious repository contains files named `..exe` and `cygpath.exe`, and `cygpath.exe` is not found in `PATH`, the `..exe` program will be executed when certain Git LFS commands are run. More generally, if the current working directory contains any file with a base name of `.` and a file extension from `PATHEXT` (except `.bat` and `.cmd`), and also contains another file with the same base name as a program Git LFS intends to execute (such as `git`, `cygpath`, or `uname`) and any file extension from `PATHEXT` (including `.bat` and `.cmd`), then, on Windows, when Git LFS attempts to execute the intended program the `..exe`, `..com`, etc., file will be executed instead, but only if the intended program is not found in any directory listed in `PATH`. The vulnerability occurs because when Git LFS detects that the program it intends to run does not exist in any directory listed in `PATH` then Git LFS passes an empty string as the executable file path to the Go `os/exec` package, which contains a bug such that, on Windows, it prepends the name of the current working directory (i.e., `.`) to the empty string without adding a path separator, and as a result searches in that directory for a file w…