# CVE-2026-4131: Cross-site request forgery in WP Responsive Popup + Optin

> Attackers can trick admins into updating plugin settings, enabling stored XSS via image URL parameter due to missing CSRF protection.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **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:** 22 Apr 2026
- **Updated:** 22 Apr 2026
- **Also known as:** GHSA-mjqc-rj22-4rf2

## What is CVE-2026-4131?

CVE-2026-4131 is a medium-severity vulnerability in sphex1987 WP Responsive Popup + Optin, published on 22 Apr 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 WP Responsive Popup + Optin plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to and including 1.4. This is due to the settings form on the admin page (wpo_admin_page.php) lacking nonce generation (wp_nonce_field) and verification (wp_verify_nonce/check_admin_referer). This makes it possible for unauthenticated attackers to update all plugin settings including the 'wpo_image_url' parameter via a forged request, granted they can trick a site administrator into performing an action such as clicking a link.

Weakness: CWE-352 (Cross-Site Request Forgery)

## Which versions are affected by CVE-2026-4131?


## How do I fix CVE-2026-4131?

No fix has been published for CVE-2026-4131 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-4131 being exploited?

There is no known exploitation of CVE-2026-4131 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4131 and fix it if it is affected.

What it is: CVE-2026-4131 is a medium-severity vulnerability in sphex1987 WP Responsive Popup + Optin, published on 22 Apr 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: There is no known exploitation of CVE-2026-4131 in the wild and no public exploit code.

Affected product: sphex1987 WP Responsive Popup + Optin. 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-2026-4131/ (Markdown: https://insights.sbomify.com/CVE-2026-4131/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4131
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4131
- OSV: https://osv.dev/vulnerability/CVE-2026-4131

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4131/
Summaries are generated and may contain mistakes; the official description above is the record.