A .vcxproj file is an XML-based Visual C++ project file used by Visual Studio and MSBuild. It defines how a C++ project is built: source files, compiler flags, linker settings, dependencies, and imported build logic such as .props and .targets files.
In cyber security, .vcxproj files matter because they are part of the trusted build chain. If an attacker can modify one, they may change what gets compiled, add unexpected build steps, or pull in malicious imports that run during the build process. That makes the file a supply-chain target, especially in shared repositories and developer workstations.