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MEDIUM severity

CVE-2021-36788 — yoast_seo

MEDIUMFix: Yoast/Yoast-SEO-for-TYPO3@a8278da

CVE-2021-36788 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in yoast-seo-for-typo3/yoast_seo. A fix is available for yoast-seo-for-typo3/yoast_seo — see the affected versions and patch details below.

Cross-site Scripting in the yoast_seo TYPO3 extension

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs39th percentile — riskier than 39% of all scored CVEsHighest risk
0.00%0.32%0.65%0.97%0.3%0.5%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-36788 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐘yoast-seo-for-typo3/yoast_seo

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

The extension fails to properly encode user input for output in HTML context. A TYPO3 backend user account is required to exploit the vulnerability.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistyoast-seo-for-typo3/yoast_seoall versions7.2.3composer require yoast-seo-for-typo3/yoast_seo:^7.2.3

Affected Products

1 product · 1 configurations
Application
yoast seoyoast
< 7.2.3
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yoast-seo-for-typo3/yoast_seo, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update yoast-seo-for-typo3/yoast_seo to 7.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-36788 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

The extension fails to properly encode user input for output in HTML context. A TYPO3 backend user account is required to exploit the vulnerability.
O3 Security · Impact-Aware SCA

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CVE-2021-36788: yoast_seo — Fixed in 7.2.3