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

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-04-05 · updated 2026-06-17
Weakness: CWE-79

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.

Affected products

Yoast SEO: Local: before 3.4.1 — fixed in 3.4.1

How to fix

Upgrade to a fixed version: Yoast SEO: Local 3.4.1. Check the vendor advisory for mitigations.

References

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

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