Patched code sample

import os

class CliCommunicationProtocol:
    """
    This example class demonstrates the conceptual fix for a vulnerability
    where the entire process environment was passed to a subprocess.
    """

    def _prepare_environment(self):
        """
        Prepares a sanitized environment dictionary for a subprocess.

        This method represents the fix for the described vulnerability. Instead of
        passing a full copy of `os.environ`, it creates a new, minimal
        dictionary containing only explicitly whitelisted variables. This
        prevents sensitive information (API keys, passwords, etc.) from
        leaking to the subprocess.
        """
        # Define a whitelist of environment variables that are considered safe
        # and necessary for the CLI subprocess to function correctly.
        allowed_vars = [
            'PATH',
            'HOME',
            'LANG',
            'LC_ALL',
            'LC_CTYPE',
        ]

        sanitized_env = {}
        for var_name in allowed_vars:
            if var_name in os.environ:
                sanitized_env[var_name] = os.environ[var_name]

        # The returned dictionary would then be passed to the `env` parameter
        # of a call like `subprocess.run()` or `subprocess.Popen()`.
        return sanitized_env