CVE-2025-9540Public exploitNetwork attack vector

Stored XSS via unsanitized Markdown link URI

Published Sep 22, 2025 · Updated Sep 22, 2025

Stored XSS in Pierre-Henri Lavigne Markup Markdown before 3.20.10 allows remote authenticated users to run JavaScript via Markdown links. The frontend Markdown rendering path converts a saved link with a javascript: URI into a clickable link without applying WordPress content sanitization. Contributor access is required to save the payload, and a viewer must click the rendered link for the script to execute in the site's browser context.

CVSS severity4.7
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 Pierre-Henri Lavigne Markup Markdown before 3.20.10 allows remote authenticated users to run JavaScript via Markdown links. The frontend Markdown rendering path converts a saved link with a javascript: URI into a clickable link without applying WordPress content sanitization. Contributor access is required to save the payload, and a viewer must click the rendered link for the script to execute in the site's browser context.

The record

CVE
CVE-2025-9540
Published
Sep 22, 2025
Updated
Sep 22, 2025
Vendor
Pierre-Henri Lavigne
Product
Markup Markdown
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 22, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 2025Record 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 <3.20.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Pierre-Henri Lavigne · Markup Markdownversion=0 <3.20.10

Published CVSS scores

4.7CISA-ADPCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L

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 exploitPublished

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

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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