CVE-2026-59711Public exploitNetwork attack vector

Cross-site scripting via unescaped metadata title

Published Jul 6, 2026 · Updated Jul 6, 2026

Cross-site scripting in Showdown 2.1.0 and earlier allows remote attackers to execute JavaScript via crafted Markdown frontmatter. With metadata and completeHTMLDocument enabled, metadata.js leaves angle brackets unescaped and completeHTMLDocument.js concatenates the title into the HTML title element. Execution occurs when an application renders attacker-controlled Markdown as a complete page and a user loads the generated HTML, allowing script access within that page's origin.

CVSS severity5.3
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Showdown 2.1.0 and earlier allows remote attackers to execute JavaScript via crafted Markdown frontmatter. With metadata and completeHTMLDocument enabled, metadata.js leaves angle brackets unescaped and completeHTMLDocument.js concatenates the title into the HTML title element. Execution occurs when an application renders attacker-controlled Markdown as a complete page and a user loads the generated HTML, allowing script access within that page's origin.

The record

CVE
CVE-2026-59711
Published
Jul 6, 2026
Updated
Jul 6, 2026
Vendor
ShowdownJS
Product
Showdown
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 6, 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 <=2.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ShowdownJS · Showdownversion=0 <=2.1.0

Published CVSS scores

6.1VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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