Executive brief
Shopper Framework is a headless e-commerce management system that handles administrative discount creation and order calculation. The system accepts negative discount values through the admin interface without validation, allowing attackers with admin privileges to create discounts with large negative amounts (e.g., -$99,999,999). These malformed discounts propagate through the pricing pipeline and cause incorrect order totals by inverting the discount effect, resulting in inflated order amounts rather than discounts.
Technical details
The vulnerability is a business logic flaw stemming from improper input validation (CWE-20). The DiscountCalculator.php component accepts any numeric discount value without enforcing the logical constraint that discounts must be positive. Negative values are persisted to the sh_discounts table and propagate through Calculate.php where they are subtracted from the subtotal. Because the code performs subtraction (subtotal - discountTotal), a negative discount results in subtraction of a negative number, effectively adding the absolute value back to the order total. For example, with subtotal 10000 and discountTotal -5000, the calculation becomes 10000 - (-5000) = 15000. Administrative privilege is required to exploit this, as the discount creation interface is restricted to authenticated administrators. The vulnerability was patched in version 2.9.0 with server-side validation enforcing positive discount values.
Affected products
- Shopper Labs Shopper Framework < 2.9.0
Timeline
- 2026-06-22: disclosed: Vulnerability published to GitHub Advisory Database
- 2026-09-11: patched: Fix released in version 2.9.0