# CVE-2021-36851: WordPress Testimonial Slider plugin <= 3.5.8.3 - Cross-Site Scripting (XSS) vulnerability

> Authenticated attackers can inject malicious scripts via color parameters in the Testimonial Slider plugin, potentially compromising user sessions.

- **Severity:** Medium 4.1 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Apr 2022
- **Updated:** 28 Apr 2026
- **Also known as:** GHSA-rjq3-c2jr-r9rq

## What is CVE-2021-36851?

CVE-2021-36851 is a medium-severity cross-site scripting vulnerability in Web-Settler Testimonial Slider – Free Testimonials Slider Plugin (WordPress plugin), published on 4 Apr 2022. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Authenticated (editor or higher user role) Cross-Site Scripting (XSS) vulnerability in Web-Settler Testimonial Slider – Free Testimonials Slider Plugin (WordPress plugin) via parameters mpsp_posts_bg_color, mpsp_posts_description_color, mpsp_slide_nav_button_color.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2021-36851?

It affects 1 product.


Products: Web-Settler Testimonial Slider.

## How do I fix CVE-2021-36851?

No fix has been published for CVE-2021-36851 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-36851 being exploited?

There is no known exploitation of CVE-2021-36851 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-36851 and fix it if it is affected.

What it is: CVE-2021-36851 is a medium-severity cross-site scripting vulnerability in Web-Settler Testimonial Slider – Free Testimonials Slider Plugin (WordPress plugin), published on 4 Apr 2022. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-36851 in the wild and no public exploit code.

Affected product: Web-Settler Testimonial Slider – Free Testimonials Slider Plugin (WordPress plugin). 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-2021-36851/ (Markdown: https://insights.sbomify.com/CVE-2021-36851/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36851
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36851
- OSV: https://osv.dev/vulnerability/CVE-2021-36851

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-36851/
Summaries are generated and may contain mistakes; the official description above is the record.