simple-git, an interface for running git commands in any node.js application, enables applications to execute Git operations from JavaScript. From 3.15.0 until 4.0.1, the default blockUnsafeOperationsPlugin does not classify trailer..cmd as unsafe configuration. An application that passes attacker-controlled values through SimpleGitOptions.config or inline -c arguments can therefore allow Git to invoke an attacker-selected shell command when git interpret-trailers processes the configured trailer. The command executes with the operating-system identity and permissions of the Node.js process. This issue is fixed in 4.0.1.