Language: Python
Label: safe
CWE: CWE-203 \u2014 Observable Discrepancy
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.

Code:
def handle_refund(notification: Dict[str, Any], _gateway_config: GatewayConfig):
    payment = get_payment(notification.get("merchantReference"))
    if not payment:
        return
    transaction_id = notification.get("pspReference")
    transaction = get_transaction(payment, transaction_id, TransactionKind.REFUND)
    if transaction and transaction.is_success:
        # it is already refunded
        return
    new_transaction = create_new_transaction(
        notification, payment, TransactionKind.REFUND
    )
    gateway_postprocess(new_transaction, payment)

    success_msg = f"Adyen: The refund {transaction_id} request was successful."
    failed_msg = f"Adyen: The refund {transaction_id} request failed."
    create_payment_notification_for_order(
        payment, success_msg, failed_msg, transaction.is_success
    )