The WordPress Simple Shopping Cart plugin, widely used for e-commerce functionality on WordPress sites, suffers from a logic flaw identified as CVE-2025-3530 (CWE-472: External Control of Assumed-Immutable Web Parameter). The vulnerability stems from the plugin's inconsistent handling of parameters during the cart addition process. Specifically, the plugin uses the parameter 'product_tmp_two' to compute a security hash intended to prevent price tampering, while simultaneously using a different parameter, 'wspsc_product', to display product information to the user. This discrepancy allows an attacker to manipulate the 'wspsc_product' parameter to substitute details of a cheaper product while the security hash is computed against the original or a different parameter, effectively bypassing price verification. Because the vulnerability requires no authentication or user interaction, an attacker can remotely exploit this flaw to purchase expensive items at lower prices or even for free by submitting crafted requests. The vulnerability affects all versions up to and including 5.1.2 of the plugin. Although no known exploits have been reported in the wild, the CVSS 3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N) reflects a high impact on integrity with network vector, low attack complexity, and no privileges or user interaction required. This vulnerability can lead to significant financial losses, undermine trust in the e-commerce platform, and disrupt business operations. The root cause is a failure to consistently validate and bind parameters used for security checks and display, allowing external control over parameters assumed immutable by the system.

The primary impact of CVE-2025-3530 is on the integrity of e-commerce transactions, allowing attackers to manipulate product prices and bypass payment for higher-priced items. This can result in direct financial losses for merchants using the affected plugin. Additionally, the exploitation of this vulnerability can damage customer trust and brand reputation, potentially leading to loss of business. Since the attack requires no authentication or user interaction, it can be automated and scaled, increasing the risk of widespread abuse. The vulnerability does not affect confidentiality or availability directly but compromises the transactional integrity critical to online commerce. Organizations relying on this plugin for payment processing or order management may face significant operational disruptions and revenue loss if exploited. Furthermore, attackers could use this flaw to conduct fraudulent purchases, complicating chargebacks and fraud detection efforts.

To mitigate CVE-2025-3530, organizations should immediately update the WordPress Simple Shopping Cart plugin to a patched version once available. In the absence of an official patch, administrators should implement strict input validation and ensure consistent use of parameters for both security hash computation and product display. Specifically, the plugin code should be reviewed and modified to bind the same parameter for price verification and display, eliminating the possibility of parameter substitution. Employing web application firewalls (WAFs) with custom rules to detect and block anomalous parameter tampering attempts can provide temporary protection. Monitoring transaction logs for unusual patterns, such as repeated low-price purchases of high-value items, can help detect exploitation attempts. Additionally, restricting access to the cart addition endpoint via rate limiting or CAPTCHA challenges may reduce automated abuse. Finally, organizations should consider alternative e-commerce plugins with robust security practices if timely patching is not feasible.