# CVE-2026-16621: Payment Gateway for PayPal on WooCommerce < 9.2.1 - Unauthenticated Payment Bypass via PayPal Advanced Return Handler

> Unauthenticated attackers can mark arbitrary orders as paid without payment by bypassing verification in the PayPal return handler.

- **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:** 12 Aug 2026
- **Updated:** 12 Aug 2026
- **Also known as:** GHSA-g8f7-gp6h-9f2x

## What is CVE-2026-16621?

CVE-2026-16621 is a medium-severity vulnerability in Unknown Payment Gateway for PayPal on WooCommerce, published on 12 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Payment Gateway for PayPal on WooCommerce WordPress plugin before 9.2.1 does not verify that payment actually succeeded before completing an order in its PayPal return handler: it reads attacker-controlled parameters, performs no amount comparison and no order-ownership check, and completes the order even when the server-side gateway verification fails, allowing an unauthenticated attacker to mark arbitrary orders as paid without paying.

## Which versions are affected by CVE-2026-16621?


## How do I fix CVE-2026-16621?

No fix has been published for CVE-2026-16621 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-16621 being exploited?

There is no known exploitation of CVE-2026-16621 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-16621 and fix it if it is affected.

What it is: CVE-2026-16621 is a medium-severity vulnerability in Unknown Payment Gateway for PayPal on WooCommerce, published on 12 Aug 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-2026-16621 in the wild and no public exploit code.

Affected product: Unknown Payment Gateway for PayPal on WooCommerce. 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-2026-16621/ (Markdown: https://insights.sbomify.com/CVE-2026-16621/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-16621
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16621
- OSV: https://osv.dev/vulnerability/CVE-2026-16621

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-16621/
Summaries are generated and may contain mistakes; the official description above is the record.