The backmeup npm package is vulnerable to OS command injection due to unsafe shell command string construction. It directly concatenates user-supplied option values (name, source, destination, filter) into shell command strings without sanitizing shell metacharacters. The package executes these strings via ssh2-exec, either locally through child_process or remotely via SSH. Path normalization functions (path.normalize, path.join) are used but do not neutralize dangerous shell metacharacters such as semicolons, pipes, ampersands, backticks, and newlines. An attacker who can influence any of the option values can achieve arbitrary OS command execution on the backup host or the remote SSH target. This represents a classic CWE-78 OS command injection flaw in a supply chain dependency.