# CVE-2026-16038: MStore API < 4.21.0 - Unauthenticated Payment Bypass via Multiple Payment Gateways

> Unauthenticated attackers can bypass payment verification to mark orders as paid, obtaining goods or services for free.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Aug 2026
- **Updated:** 7 Aug 2026
- **Also known as:** GHSA-5xp8-jj53-535m

## What is CVE-2026-16038?

CVE-2026-16038 is a critical vulnerability in Unknown MStore API, published on 7 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The MStore API  WordPress plugin before 4.21.0 does not verify the payment with the payment gateway before marking an order as paid on several of its payment-completion endpoints, allowing an unauthenticated attacker to mark an arbitrary order fully paid without paying and obtain goods or services for free.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-16038?


## How do I fix CVE-2026-16038?

No fix has been published for CVE-2026-16038 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-16038 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-16038 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-16038 and fix it if it is affected.

What it is: CVE-2026-16038 is a critical vulnerability in Unknown MStore API, published on 7 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-16038 exists.

Affected product: Unknown MStore API. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-16038/ (Markdown: https://insights.sbomify.com/CVE-2026-16038/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-16038
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16038
- OSV: https://osv.dev/vulnerability/CVE-2026-16038

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-16038/
Summaries are generated and may contain mistakes; the official description above is the record.