# CVE-2026-11855: Simple Membership < 4.7.5 - Unauthenticated Stored XSS via Stripe Webhook API Version

> Unauthenticated attackers can inject scripts via Stripe webhooks in Simple Membership plugin, leading to admin session hijacking.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 6 Jul 2026
- **Updated:** 6 Jul 2026
- **Also known as:** GHSA-xmqj-cv3v-f292

## What is CVE-2026-11855?

CVE-2026-11855 is a high-severity cross-site scripting vulnerability in Unknown Simple Membership, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

The Simple Membership WordPress plugin before 4.7.5 does not verify the authenticity of Stripe webhook requests when no signing secret is configured, nor escape a value taken from them before outputting it in an administrator notice, allowing unauthenticated attackers to inject arbitrary web scripts that execute in the context of a logged-in administrator.

## Which versions are affected by CVE-2026-11855?


## How do I fix CVE-2026-11855?

No fix has been published for CVE-2026-11855 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-11855 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-11855 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11855 and fix it if it is affected.

What it is: CVE-2026-11855 is a high-severity cross-site scripting vulnerability in Unknown Simple Membership, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-11855 exists.

Affected product: Unknown Simple Membership. 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-2026-11855/ (Markdown: https://insights.sbomify.com/CVE-2026-11855/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11855
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11855
- OSV: https://osv.dev/vulnerability/CVE-2026-11855

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-11855/
Summaries are generated and may contain mistakes; the official description above is the record.