CVE-2026-56831 — shopper / framework
Improper Input ValidationSummary
The Shopper Framework discount management functionality accepts negative discount values without server-side validation.
It was confirmed that negative fixed-amount discounts can be created through the administrative interface, persisted to the database, and subsequently processed by the cart/order calculation pipeline.
The application appears to assume that discount values are always positive but does not enforce this assumption during creation, storage, or calculation.
As a result, malformed discount records can influence financial calculations and produce unintended order totals.
Affected Product
Package: shopper/framework
Version Tested: 2.8.1
Vulnerability Type
- Business Logic Vulnerability
- Improper Input Validation (CWE-20)
Description
While reviewing the discount functionality, it was discovered that the application accepts negative discount values through the administrative interface.
Example values tested:
-50.00
-99,999,999.00
The application accepted these values without validation and stored them in the database.
Example records observed in the sh_discounts table:
1 | QCZ5Y3HESM | fixed_amount | -5000
4 | TOZKAHCB4S | fixed_amount | -9999999900
This demonstrates that negative discount values are successfully persisted.
Steps to Reproduce
1. Create a Discount
Login as an administrator.
Navigate to:
/cpanel/discounts
Create a new discount with the following values:
Type: fixed_amount
Value: -99999999
Save the discount.
2. Observe Successful Creation
The discount is accepted by the application and displayed in the administration interface.
Example:
Code: TOZKAHCB4S
Amount: -$99,999,999.00
3. Verify Database Persistence
Inspect the database:
select * from sh_discounts;
Observed entry:
TOZKAHCB4S | fixed_amount | -9999999900
Technical Analysis
Discount Calculation
File:
vendor/shopper/cart/src/Discounts/DiscountCalculator.php
Observed code:
$fixedAmount = $discount->value;
The value is later processed without validation:
$fixedAmount = min($fixedAmount, $applicableSubtotal);
When a negative value is supplied:
min(-9999999900, 10000)
returns:
-9999999900
allowing the negative value to continue through the calculation pipeline.
The resulting adjustment values are inserted into the database:
CartLineAdjustment::query()->insert($adjustments);
No validation was identified to ensure that discount amounts are positive before calculations occur.
Final Total Calculation
File:
vendor/shopper/cart/src/Pipelines/Calculate.php
Observed logic:
$context->total = max(
0,
$context->taxInclusive
? $context->subtotal - $context->discountTotal
: $context->subtotal - $context->discountTotal + $context->taxTotal
);
Because negative discount values are allowed to reach this stage, financial calculations are performed using malformed discount data.
Example:
Subtotal = 10000
DiscountTotal = -5000
Resulting calculation:
10000 - (-5000)
Result:
15000
This demonstrates that negative discount values directly affect order total calculations.
Impact
The following was confirmed:
- Negative discount values are accepted.
- Negative discount values are persisted.
- Negative discount values are processed by the discount calculation engine.
- Negative discount values affect order total calculations.
Potential consequences include:
- Incorrect pricing calculations.
- Financial data integrity issues.
- Unexpected order totals.
- Violated assumptions within downstream pricing logic.
- Future vulnerabilities if additional components assume discount values are always positive.
Because Shopper is a headless e-commerce administration framework and does not ship with a customer-facing storefront, it was not verified a customer-facing exploitation path.
However, malformed discount records currently propagate through pricing calculations without validation.
Recommendation
Implement server-side validation enforcing positive discount values before persistence and before entering the calculation pipeline.
Suggested validation:
Fixed Amount Discounts
value > 0
Percentage Discounts
0 < value <= 100
Additionally, existing discount records should be validated before calculation to prevent malformed data from influencing pricing logic.
Environment
Shopper Framework 2.8.1
Laravel 12.61.1
PHP 8.4.16
SQLite
| Software | Affected versions |
|---|---|
shopper / framework
|
< 2.9.0 |
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