CVE-2026-2951Network attack vector

Stored XSS via regex-based block HTML sanitization

Published Apr 23, 2026 · Updated Apr 23, 2026

Stored XSS in Acme Information Technology Gutentor 3.5.5 and earlier allows remote authenticated users to inject scripts into pages. The Gutentor block HTML sanitizer uses fragile regular-expression filtering instead of a strict element-and-attribute allowlist, leaving attacker-controlled markup insufficiently sanitized and escaped. Contributor-level access is required to save the payload, and the script runs in a user's browser when the injected page is opened.

CVSS severity5.4
Medium
EPSS probability0.17%
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 Acme Information Technology Gutentor 3.5.5 and earlier allows remote authenticated users to inject scripts into pages. The Gutentor block HTML sanitizer uses fragile regular-expression filtering instead of a strict element-and-attribute allowlist, leaving attacker-controlled markup insufficiently sanitized and escaped. Contributor-level access is required to save the payload, and the script runs in a user's browser when the injected page is opened.

The record

CVE
CVE-2026-2951
Published
Apr 23, 2026
Updated
Apr 23, 2026
Vendor
Acme Information Technology
Product
Gutentor – Gutenberg Blocks – Page Builder for Gutenberg Editor
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 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 <=3.5.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Acme Information Technology · Gutentor – Gutenberg Blocks – Page Builder for Gutenberg Editorversion=0 <=3.5.5

Published CVSS scores

5.4WordfenceCVSS:3.1/AV:N/AC:L/PR:L/UI:R/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')
T1059.007JavaScript/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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