CVE-2025-3530: WordPress Shopping Cart Auth Bypass Flaw

CVE-2025-3530 Overview

CVE-2025-3530 is a business logic vulnerability affecting the WordPress Simple Shopping Cart plugin that enables unauthenticated attackers to manipulate product prices during the checkout process. The vulnerability exists due to a logic flaw where inconsistent parameters are used during the cart addition process, allowing attackers to bypass payment validation and purchase expensive items at reduced prices.

Critical Impact

Unauthenticated attackers can exploit this price manipulation flaw to bypass payment for expensive items by substituting details from cheaper products, resulting in direct financial losses for e-commerce sites using this plugin.

Affected Products

• WordPress Simple Shopping Cart plugin versions up to and including 5.1.2
• WordPress sites utilizing the Simple PayPal Shopping Cart functionality
• E-commerce implementations relying on the affected plugin's price verification mechanism

Discovery Timeline

• April 23, 2025 - CVE-2025-3530 published to NVD
• April 15, 2026 - Last updated in NVD database

Technical Details for CVE-2025-3530

Vulnerability Analysis

This vulnerability is classified under CWE-472 (External Control of Assumed-Immutable Web Parameter), a business logic flaw that allows attackers to manipulate data the application assumes cannot be modified. The core issue lies in the plugin's cart addition workflow where two different parameters serve conflicting purposes during the same transaction.

The plugin uses the product_tmp_two parameter for computing a security hash to prevent price tampering, while simultaneously using wspsc_product to display and process the actual product details. This inconsistency creates a window of opportunity where an attacker can provide valid security hash information from a low-priced product while substituting the display product with a higher-priced item.

The attack requires no authentication and can be executed remotely over the network. While it does not compromise confidentiality or system availability, the integrity impact is significant as it enables complete bypass of the payment verification mechanism.

Root Cause

The root cause is the inconsistent handling of product identification parameters within the cart addition logic. The security hash validation occurs against one parameter (product_tmp_two) while the actual product details displayed and processed are pulled from a different parameter (wspsc_product). This architectural flaw means the integrity check does not actually validate the product that gets added to the cart and processed through checkout.

The relevant code sections can be found in wp_shopping_cart.php around lines 156, 165, 171, and 261, where the parameter handling diverges and creates the exploitable condition.

Attack Vector

An unauthenticated attacker can exploit this vulnerability by crafting malicious requests that supply a valid security hash computed against a cheap product's details via product_tmp_two, while simultaneously providing the name and details of an expensive product via wspsc_product. The plugin's validation logic accepts the hash as valid (since it matches the cheap product), but processes the expensive product for the actual purchase.

The attack flow involves:

1. Identifying a low-priced product and capturing its security hash parameters
2. Crafting a request that combines the valid hash with the target expensive product's identifiers
3. Submitting the manipulated cart addition request
4. Completing checkout at the fraudulently reduced price

For technical implementation details, refer to the WordPress Plugin Source Code and the Wordfence Vulnerability Report.

Detection Methods for CVE-2025-3530

Indicators of Compromise

• Cart addition requests where product_tmp_two and wspsc_product parameters contain different product identifiers
• Orders where the final payment amount does not match the expected price for the purchased product
• Unusual patterns of high-value products being purchased at low-value prices
• POST requests to cart endpoints with manipulated or mismatched parameter values

Detection Strategies

• Implement server-side logging to capture and correlate both product_tmp_two and wspsc_product parameter values for each cart addition
• Create alerts for orders where the product name differs from the product used in hash validation
• Deploy Web Application Firewall (WAF) rules to detect parameter mismatches in cart operations
• Enable transaction monitoring to flag orders with suspicious price-to-product discrepancies

Monitoring Recommendations

• Monitor e-commerce transaction logs for orders where payment amounts appear inconsistent with purchased items
• Review access logs for repeated cart manipulation attempts from the same IP addresses
• Implement real-time alerting on cart addition endpoints with anomaly detection for parameter tampering
• Audit completed orders periodically to identify any successful exploitation attempts

How to Mitigate CVE-2025-3530

Immediate Actions Required

• Update the WordPress Simple Shopping Cart plugin to the latest patched version immediately
• Review recent transaction history for signs of price manipulation exploitation
• Implement temporary server-side validation to ensure product consistency across all cart parameters
• Consider temporarily disabling the plugin if an immediate update is not possible

Patch Information

A security patch addressing this vulnerability has been released. The fix ensures consistent parameter usage throughout the cart addition and checkout process, preventing the parameter substitution attack. The patch can be obtained through the WordPress Plugin Changeset. Site administrators should update to a version newer than 5.1.2 to remediate this vulnerability.

Workarounds

• Implement server-side middleware to validate that product identifiers match across all cart-related parameters before processing
• Deploy WAF rules to block requests where product_tmp_two and wspsc_product contain mismatched values
• Add custom validation hooks in WordPress to verify product-price consistency before checkout completion
• Consider using alternative shopping cart plugins until the update can be applied

# Verify current plugin version
wp plugin list --name=wordpress-simple-paypal-shopping-cart --fields=name,version

# Update to latest patched version
wp plugin update wordpress-simple-paypal-shopping-cart

# Verify update was successful
wp plugin list --name=wordpress-simple-paypal-shopping-cart --fields=name,version,update_version