CVE-2024-35218Network attack vector

Stored XSS via unsanitized Markdown preview

Published May 21, 2024 · Updated Aug 2, 2024

Stored XSS in the Markdown editor of Umbraco CMS allows remote authenticated users to run script in a backoffice user's browser. The Markdown property value editor persisted submitted Markdown without sanitizing it, so the preview pane rendered attacker-controlled HTML and script. Backoffice access is required to store the payload, and another backoffice user must open the affected content preview, exposing data available in that user's browser session.

CVSS severity4.2
Medium
EPSS probability0.35%
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 the Markdown editor of Umbraco CMS allows remote authenticated users to run script in a backoffice user's browser. The Markdown property value editor persisted submitted Markdown without sanitizing it, so the preview pane rendered attacker-controlled HTML and script. Backoffice access is required to store the payload, and another backoffice user must open the affected content preview, exposing data available in that user's browser session.

The record

CVE
CVE-2024-35218
Published
May 21, 2024
Updated
Aug 2, 2024
Vendor
Umbraco
Product
Umbraco CMS
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>= 10.0.0, < 10.8.4
  2. Affected versionversion=>= 12.0.0, < 12.3.7
  3. Affected versionversion=>= 13.0.0, < 13.1.1
  4. Affected versionversion=>= 8.0.0, < 8.18.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Umbraco · Umbraco CMSversion=>= 10.0.0, < 10.8.4; version=>= 12.0.0, < 12.3.7; version=>= 13.0.0, < 13.1.1; version=>= 8.0.0, < 8.18.13

Published CVSS scores

4.2GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:N/A:N
4.8NISTCVSS:3.1/AV:N/AC:L/PR:H/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 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/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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