CVE-2026-104641 in Simple Shopping Cart Plugin
Summary
by MITRE • 10/21/2026
The Simple Shopping Cart WordPress plugin before 5.3.3 does not verify that a PayPal payment notification is for a payment received by the site owner's PayPal account in its default configuration, allowing unauthenticated attackers to have their orders marked as paid using a payment made to an account they control.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified within versions of the Simple Shopping Cart WordPress plugin prior to 5.3.3 represents a critical failure in transaction verification logic, specifically concerning how external payment gateways are integrated with the application's order management system. In e-commerce environments relying on third-party processors like PayPal, it is imperative that the backend service validates incoming notifications against specific criteria unique to the merchant account. The flaw arises because the plugin fails to verify that a PayPal Payment Notification IPN message corresponds to a transaction received by the site owner’s designated PayPal business account. Instead of cross-referencing the receiver email or account ID embedded in the notification with the configured merchant credentials, the application accepts any validly signed payment confirmation regardless of which recipient account actually processed the funds. This oversight creates a significant gap in the integrity checks required to maintain accurate financial records and order statuses within the WordPress ecosystem.
From an operational perspective, this defect allows unauthenticated attackers to manipulate the state of orders without possessing legitimate credentials or completing actual payments intended for the merchant. By initiating a payment through their own PayPal account and manipulating the notification parameters sent back to the vulnerable plugin, an attacker can force the system to mark any order as paid successfully. This capability effectively bypasses the financial gatekeeping mechanism of the store, enabling fraudulent acquisition of digital goods, services, or physical inventory that would otherwise require monetary exchange. The impact extends beyond simple revenue loss; it compromises the reliability of sales data and customer records, potentially leading to inventory discrepancies and reputational damage if customers receive items without having paid the merchant.
This vulnerability aligns with CWE-345, which describes Insufficient Verification of Data Authenticity, as the application does not adequately verify that incoming data originates from a trusted source or matches expected parameters for its specific context. Furthermore, it relates to CWE-862, Missing Authorization, because an unauthenticated actor can perform actions restricted to legitimate transactions by exploiting the lack of proper validation logic rather than breaking into user accounts directly. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior facilitates techniques associated with Account Manipulation and potentially Financial Fraud, where adversaries exploit trust relationships between systems to gain unauthorized benefits or disrupt business operations through data integrity violations.
Mitigation for this issue requires immediate updating to version 5.3.3 or later of the Simple Shopping Cart plugin, which addresses these validation gaps by implementing strict checks on receiver account identifiers during IPN processing. Administrators should also ensure that their WordPress environment is fully patched and that all plugins are kept up to date with security releases from official repositories. Additionally, implementing server-side logging for payment notifications can aid in detecting anomalous patterns where multiple orders are marked as paid simultaneously or by unusual user agents, providing an additional layer of monitoring against exploitation attempts while the software update is applied.