CVE-2026-113468 in Shop Plugin
Summary
by MITRE • 10/20/2026
The payment notification endpoint for PayPal accepts incoming data without verifying that it comes from the payment provider. Any site visitor can overwrite the stored payment notification of an order that is still awaiting payment with arbitrary content. This requires a page that contains the shop's order plugin. Orders that are already paid are not affected.
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Analysis
by VulDB Data Team • 10/20/2026
The vulnerability described constitutes a critical failure in input validation and source authentication within the PayPal integration module, specifically affecting the endpoint responsible for processing payment notifications. In secure software architecture, callbacks or webhooks from external financial providers must be rigorously authenticated to ensure that the data originates exclusively from the trusted entity. The flaw arises because the application accepts incoming HTTP requests intended as payment status updates without verifying digital signatures, IP addresses, or other cryptographic proofs of origin provided by PayPal. This lack of verification allows any actor with network access to the server to inject arbitrary payloads into the system under the guise of a legitimate transaction update.
The operational impact of this vulnerability is severe for e-commerce platforms relying on automated order processing workflows. Since the endpoint does not distinguish between genuine notifications from PayPal and forged requests, an attacker can manipulate the state of orders that are currently in a pending or awaiting payment status. By sending crafted HTTP POST requests to the notification endpoint with modified data fields, such as changing the transaction status from unpaid to paid or altering the amount received, the system may incorrectly mark these orders as completed. This leads directly to financial loss through unauthorized fulfillment of goods and services without actual monetary compensation. Furthermore, this manipulation can disrupt inventory management systems that rely on accurate order statuses for stock allocation, potentially leading to overselling or logistical errors.
From a classification perspective, this issue aligns with CWE-345 Insufficient Verification of Data Authenticity, as the application fails to verify that the data received is from its expected source. It also relates closely to CWE-20 Improper Input Validation, where the system does not adequately sanitize or validate incoming parameters before processing them into internal state changes. In terms of offensive security frameworks like MITRE ATT&CK, this vulnerability facilitates techniques associated with Supply Chain Compromise and Data Manipulation, allowing an adversary to alter stored data within a trusted application environment without direct exploitation of code execution flaws. The attack vector is typically remote if the endpoint is exposed over the internet, making it accessible to any external actor capable of crafting HTTP requests.
Mitigation strategies must focus on implementing robust authentication mechanisms for all incoming webhook or notification endpoints. Developers should enforce signature verification using cryptographic keys provided by PayPal, ensuring that each request includes a valid digital signature generated with the merchant's secret key. Additionally, IP address filtering can be employed to restrict access to known PayPal server ranges, although this is less secure than cryptographic validation due to potential IP changes on the provider side. It is also crucial to implement idempotency checks and transaction state machine validations within the application logic to prevent duplicate or out-of-sequence status updates from altering order states incorrectly. Regular security audits of third-party integrations are essential to ensure that such authentication gaps do not persist in production environments, thereby maintaining the integrity of financial transactions and customer data.