CVE-2026-3427Network attack vector

Stored XSS via decoded HowTo block markup

Published Mar 22, 2026 · Updated Mar 22, 2026

Stored XSS in Yoast SEO 27.1.1 and earlier allows remote authenticated users to inject scripts through a HowTo block's jsonText attribute. The HowTo schema generator decodes HTML entities in step descriptions but fails to strip the resulting tags before placing jsonText in page output. Contributor-level access is sufficient, and the stored script executes when an affected page is viewed.

CVSS severity6.4
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Yoast SEO 27.1.1 and earlier allows remote authenticated users to inject scripts through a HowTo block's jsonText attribute. The HowTo schema generator decodes HTML entities in step descriptions but fails to strip the resulting tags before placing jsonText in page output. Contributor-level access is sufficient, and the stored script executes when an affected page is viewed.

The record

CVE
CVE-2026-3427
Published
Mar 22, 2026
Updated
Mar 22, 2026
Vendor
Yoast
Product
Yoast SEO
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=* <=27.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Yoast · Yoast SEOversion=* <=27.1.1

Published CVSS scores

6.4WordfenceCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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