Patched code sample

def sanitize_input(data):
    """
    Sanitizes the input data to prevent class pollution.

    Args:
        data: The input data (e.g., a dictionary) to be sanitized.

    Returns:
        A sanitized version of the input data, or the original data if no
        malicious patterns are detected.  Returns an empty dictionary if
        the input is malicious.
    """
    if not isinstance(data, dict):
        return data

    # Check for potentially malicious keys.  This example focuses on keys
    # that could target built-in Python classes or sensitive Mesop modules.
    # The actual list of prohibited keys would depend on the specific
    # internal structure of Mesop and the modules it uses.
    prohibited_keys = ["__class__", "__mro__", "__base__", "object", "type"]

    for key in data:
        if key in prohibited_keys:
            print(f"Detected prohibited key: {key}.  Input rejected.")
            return {}  # Or raise an exception: raise ValueError("Invalid input")

        # Recursively sanitize nested dictionaries
        if isinstance(data[key], dict):
            data[key] = sanitize_input(data[key])

    return data


def process_user_input(user_input):
    """
    Processes user input after sanitization.

    Args:
        user_input: The user input dictionary.

    Returns:
        The processed user input, or None if the input was invalid.
    """
    sanitized_input = sanitize_input(user_input)

    if not sanitized_input:
        print("Invalid user input. Processing stopped.")
        return None

    # Now you can safely use the sanitized_input.
    # Example usage:
    # For example, create a class where attributes are set based on the user input.

    class UserData:
        def __init__(self, data):
            for key, value in data.items():
                setattr(self, key, value)

    try:
        user_data = UserData(sanitized_input)
        # ... further processing with user_data ...
        return user_data

    except Exception as e:  # Catch errors that might still occur during object creation
        print(f"Error processing user input: {e}")
        return None


# Example usage (Demonstrates mitigation)
if __name__ == "__main__":
    # Malicious input example attempting to pollute the class
    malicious_input = {"__class__": {"__mro__": [object, {"new_attribute": "malicious_value"}]}}

    # Correct usage Example
    user_input = {"username": "test_user", "email": "test@example.com"}


    result_malicious = process_user_input(malicious_input)
    result_correct = process_user_input(user_input)

    if result_malicious is None:
        print("Malicious input was correctly blocked.")
    else:
        print("Malicious input was not blocked!")


    if result_correct is not None:
        print("Correct input was processed.")
        print(f"Username: {result_correct.username}, Email: {result_correct.email}")
    else:
        print("Correct input was not processed")