CVE-2026-3604Network attack vector

Stored XSS via unescaped active-tab metadata

Published May 12, 2026 · Updated May 12, 2026

Stored XSS in Kansas City SEO WP SEO Structured Data Schema 2.8.1 and earlier allows remote authenticated users to execute scripts. The KcSeoMetaData.php metadata path stores and later renders the _kcseo_ative_tab value without sufficient sanitization or output escaping. Contributor-level access is sufficient, and the payload runs in browsers that access the injected page, enabling page-context data reads or writes.

CVSS severity4.9
Medium
EPSS probability0.23%
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 Kansas City SEO WP SEO Structured Data Schema 2.8.1 and earlier allows remote authenticated users to execute scripts. The KcSeoMetaData.php metadata path stores and later renders the _kcseo_ative_tab value without sufficient sanitization or output escaping. Contributor-level access is sufficient, and the payload runs in browsers that access the injected page, enabling page-context data reads or writes.

The record

CVE
CVE-2026-3604
Published
May 12, 2026
Updated
May 12, 2026
Vendor
Kansas City SEO
Product
WP SEO Structured Data Schema
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 12, 2026CVE publishedPublication date reported by the CVE source.
  2. May 12, 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=0 <=2.8.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Kansas City SEO · WP SEO Structured Data Schemaversion=0 <=2.8.1

Published CVSS scores

4.9WordfenceCVSS:3.1/AV:N/AC:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 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

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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