Sylius Mollie Plugin vulnerable to payment status forgery via the payment webhook
Impact
The shop payment webhook POST /{_locale}/update-payment (route
sylius_mollie_shop_payment_webhook) accepts two independent, attacker-controlled
parameters: id (the Mollie payment ID, verified against Mollie's API) and orderId (the
Sylius order ID, read directly from the database). The handler never verifies that the
Mollie payment belongs to the referenced order.
An unauthenticated attacker who holds any valid paid Mollie payment ID, for example
from a EUR 1 order they placed themselves, can submit it together with any victim
orderId. The victim's order payment is then transitioned to completed (or any other
Mollie-derived state) without any funds being transferred for that order. Sylius order IDs
are sequential integers, and the endpoint requires no authentication, CSRF token or rate
limiting, so the attack scales trivially across all pending orders.
Patches
Fixed in versions 2.2.8, 3.2.4 and 3.3.1. The webhook now binds the payment to
the order: it reads the Mollie payment ID stored server-side for that order when the payment
was created and compares it to the incoming Mollie payment ID. On mismatch the request is
acknowledged with HTTP 200 and no state change is applied. HTTP 200 is intentional,
because Mollie retries the webhook on any non-2xx response.
The stored ID lives in one of two places depending on the checkout flow, and the fix reads
both of them (mirroring CaptureAction):
payment.getDetails()['payment_mollie_id'] for the standard Shop API and Apple Pay Direct
flows, stored in CreatePaymentAction.
order.getMolliePaymentId() for the QR-code flow, which stores the ID on the order itself
(QrCodeAction).
Reading only the payment details would reject legitimate QR-code payments, because their
payment details carry no payment_mollie_id, so both sources must be consulted.
Workarounds
If you cannot upgrade immediately, patch the vulnerability at the project level by
decorating the plugin's webhook controller. The decorator checks that the incoming Mollie
id matches the id stored for that order before handing over to the original controller,
so no plugin behaviour (state machine, logging) is lost and no extra Mollie API call is
made. Works on both 2.2 and 3.x.
Step 1. Create the decorator
Create src/Controller/Mollie/SecurePaymentWebhookController.php in your Sylius project:
```php
<?php
declare(strict_types=1);
namespace App\Controller\Mollie;
use Sylius\Component\Core\Model\OrderInterface;
use Sylius\Component\Order\Repository\OrderRepositoryInterface;
use Sylius\MolliePlugin\Controller\Shop\PaymentWebhookController;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
final class SecurePaymentWebhookController
{
public function __construct(
private readonly PaymentWebhookController $inner,
private readonly OrderRepositoryInterface $orderRepository,
) {
}
public function __invoke(Request $request): Response
{
$orderId = $request->get('orderId');
$molliePaymentId = $request->get('id');
if (null === $orderId || null === $molliePaymentId) {
return ($this->inner)($request);
}
/** @var OrderInterface|null $order */
$order = $this->orderRepository->findOneBy(['id' => $orderId]);
if (null === $order) {
return ($this->inner)($request);
}
$storedMollieId = $this->resolveStoredMollieId($order);
// Reject any webhook whose Mollie id does not match the one stored for this order.
// 200 is intentional: Mollie retries on any non-2xx response.
if (null === $storedMollieId || $storedMollieId !== (string) $molliePaymentId) {
return new JsonResponse(null, Response::HTTP_OK);
}
return ($this->inner)($request);
}
private function resolveStoredMollieId(OrderInterface $order): ?string
{
$payment = $order->getLastPayment();
$fromDetails = $payment?->getDetails()['payment_mollie_id'] ?? null;
if (null !== $fromDetails && '' !== $fromDetails) {
return (string) $fromDetails;
}
// QR-code flow stores the Mollie id on the order itself.
if (method_exists($order, 'getMolliePaymentId')) {
$fromOrder = $order->getMolliePaymentId();
if (null !== $fromOrder && '' !== $fromOrder) {
return (string) $fromOrder;
}
}
return null;
}
}
```
Step 2. Register the decorator
Append to your project's config/services.yaml:
```yaml
services:
App\Contr
