CVE-2026-31889

### Summary We identified and fixed a vulnerability in the Shopware app registration flow that could, under specific conditions, allow attackers to take over the communication channel between a shop and an app. By abusing app re‑registration, an attacker could redirect app traffic to an attacker‑controlled domain and potentially obtain API credentials intended for the legitimate shop. We have no evidence that this vulnerability has been exploited. --- ### Affected Scope - All apps (public and private) that use a `registrationUrl` in their app manifest and rely on the legacy HMAC‑based registration flow. - Both on‑premise and cloud installations are affected until updated to a fixed Shopware version or protected by the latest Shopware Security Plugin. - Shopware services and first‑party apps using the affected SDKs were reviewed and patched. The vulnerability does not affect core storefront or administration authentication; it is limited to the app system’s registration and re‑registration mechanism. --- ### Impact In a successful attack, an attacker who already knows certain app‑side secrets could: - Re‑register an existing app installation with a domain under their control. - Intercept App → Shop communication and cause data tampering (“data poisoning”). - Obtain API integration credentials of the shop with the permissions granted to the app. Shop owners and app manufacturers would typically observe this as “app malfunction” rather than an obvious security issue, which increases the need for hardening. --- ### Root Cause The legacy app registration flow used HMAC‑based authentication without sufficiently binding a shop installation to its original domain. During re‑registration, the `shop-url` could be updated without proving control over the previously registered shop or domain. This made targeted hijacking of app communication feasible if an attacker possessed the relevant app‑side secret. --- ### Fix We have hardened the app registration and re‑regi