CVE-2026-35569Public exploitNetwork attack vector

Authenticated data exposure via stored SEO-field XSS

Published Apr 15, 2026 · Updated Apr 15, 2026

Stored XSS in ApostropheCMS 4.28.0 and earlier allows remote authenticated users to execute JavaScript in an authenticated viewer's browser. The @apostrophecms/seo module renders SEO Title and Meta Description values into title, meta-attribute, and JSON-LD contexts without context-appropriate escaping. An editor can store a breakout payload, but execution requires an authenticated user to view the published page; the script can issue same-session API requests and exfiltrate usernames, email addresses, and roles.

CVSS severity8.7
High
EPSS probability0.30%
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 ApostropheCMS 4.28.0 and earlier allows remote authenticated users to execute JavaScript in an authenticated viewer's browser. The @apostrophecms/seo module renders SEO Title and Meta Description values into title, meta-attribute, and JSON-LD contexts without context-appropriate escaping. An editor can store a breakout payload, but execution requires an authenticated user to view the published page; the script can issue same-session API requests and exfiltrate usernames, email addresses, and roles.

The record

CVE
CVE-2026-35569
Published
Apr 15, 2026
Updated
Apr 15, 2026
Vendor
Apostrophe Technologies
Product
ApostropheCMS
Classifications
CWE-116, CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 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=< 4.29.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Apostrophe Technologies · ApostropheCMSversion=< 4.29.0

Published CVSS scores

8.7GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/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 exploitPublished

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript/JScript

Public exploit references

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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