Sylius Mollie Plugin provides Mollie payment integration for Sylius applications. Prior to 2.2.8, 3.2.4, and 3.3.1, Sylius Mollie Plugin's POST /{_locale}/update-payment payment webhook accepts attacker-controlled id and orderId parameters but does not verify that the Mollie payment belongs to the referenced Sylius order, allowing an unauthenticated attacker with any valid paid Mollie payment ID to mark a victim order as paid without transferring funds for that order. This issue is fixed in 2.2.8, 3.2.4, and 3.3.1.

Affected: Packagist: sylius/mollie-plugin

### 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`)…