CVE-2019-7441 in PayPal Checkout Payment Gateway Plugin
Summary
by MITRE
cgi-bin/webscr?cmd=_cart in the WooCommerce PayPal Checkout Payment Gateway plugin 1.6.8 for WordPress allows Parameter Tampering in an amount parameter (such as amount_1), as demonstrated by purchasing an item for lower than the intended price.
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Analysis
by VulDB Data Team • 09/20/2025
The vulnerability identified as CVE-2019-7441 affects the WooCommerce PayPal Checkout Payment Gateway plugin version 1.6.8 for WordPress, specifically targeting the cgi-bin/webscr endpoint with the cmd=_cart parameter. This issue represents a critical parameter tampering vulnerability that directly impacts the integrity of payment transactions within e-commerce environments. The flaw exists in the payment processing logic where the amount parameter values such as amount_1 can be manipulated by malicious actors during the checkout process. The vulnerability stems from insufficient input validation and sanitization mechanisms that fail to properly validate the monetary values passed through the PayPal payment gateway integration. Attackers can exploit this weakness to alter the transaction amounts, potentially allowing them to purchase items for less than the intended price, which directly results in financial loss for merchants.
The technical implementation of this vulnerability aligns with CWE-20, which describes improper input validation, and CWE-345, which addresses insufficient verification of data integrity. The flaw operates through a classic parameter tampering attack vector where the attacker modifies the amount_1 parameter value in the payment request before it reaches the PayPal payment processing system. This type of vulnerability falls under the ATT&CK technique T1071.004, which involves application layer protocol manipulation, specifically targeting web application protocols for financial gain. The vulnerability is particularly dangerous because it occurs within the payment gateway integration layer, where transaction values are processed and validated before being transmitted to PayPal's payment processing infrastructure. The lack of proper parameter validation creates a direct pathway for attackers to manipulate the monetary values in payment requests.
The operational impact of CVE-2019-7441 extends beyond simple financial loss, as it compromises the trust model between merchants and customers within WordPress-based e-commerce platforms. When exploited, this vulnerability allows attackers to systematically undercharge for products, potentially resulting in significant revenue loss for online businesses. The vulnerability affects all WordPress sites utilizing the affected WooCommerce PayPal Checkout Payment Gateway plugin version 1.6.8, making it a widespread concern for e-commerce operators. The attack surface is particularly broad as it can be exploited by both technical and non-technical attackers, given the straightforward nature of parameter manipulation in web forms. Merchants may experience financial discrepancies, customer complaints, and potential legal issues related to unauthorized transaction modifications. The vulnerability also increases the risk of fraud and can potentially be used as a stepping stone for more sophisticated attacks targeting the broader payment ecosystem.
Mitigation strategies for this vulnerability should include immediate patching of the WooCommerce PayPal Checkout Payment Gateway plugin to version 1.6.9 or later, which contains the necessary security fixes. Organizations should implement comprehensive input validation mechanisms that verify all monetary parameters against expected ranges and formats before processing payment requests. Network monitoring solutions should be deployed to detect unusual transaction patterns that may indicate parameter tampering attempts. Additionally, merchants should consider implementing transaction approval workflows that require manual verification of high-value transactions. Security teams should establish regular vulnerability scanning procedures to identify similar issues in other third-party plugins and themes. The fix implemented in the patched version addresses the core validation issue by ensuring that amount parameters are properly sanitized and validated before being processed in the payment gateway integration. Organizations should also review their payment processing workflows to ensure that all transaction values are consistently validated and logged for audit purposes, as recommended by payment card industry standards and security frameworks.