# CVE-2026-83537: WP Express Checkout < 2.5.0 - Unauthenticated Payment Bypass via wpec_process_empty_payment

> Unauthenticated attackers can bypass payment verification in WP Express Checkout to mark orders as paid without actually paying.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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:** 9 Sep 2026
- **Updated:** 9 Sep 2026
- **Also known as:** GHSA-89f9-r4mq-rxxm

## What is CVE-2026-83537?

CVE-2026-83537 is a medium-severity vulnerability in Unknown WP Express Checkout, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The WP Express Checkout WordPress plugin before 2.5.0 does not verify server-side that a payment was actually completed before marking an order as paid, allowing unauthenticated users to forge a completed order without paying.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-83537?


## How do I fix CVE-2026-83537?

No fix has been published for CVE-2026-83537 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-83537 being exploited?

There is no known exploitation of CVE-2026-83537 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-83537 and fix it if it is affected.

What it is: CVE-2026-83537 is a medium-severity vulnerability in Unknown WP Express Checkout, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-83537 in the wild and no public exploit code.

Affected product: Unknown WP Express Checkout. 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-2026-83537/ (Markdown: https://insights.sbomify.com/CVE-2026-83537/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-83537
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-83537
- OSV: https://osv.dev/vulnerability/CVE-2026-83537

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-83537/
Summaries are generated and may contain mistakes; the official description above is the record.