CVE-2026-59711

Medium

Description

showdown contains a cross-site scripting vulnerability in metadata title handling that allows attackers to inject arbitrary HTML and JavaScript. When completeHTMLDocument option is enabled, unescaped less-than and greater-than characters in markdown frontmatter metadata are inserted directly into HTML title tags, enabling attackers to break out of the title context and execute malicious scripts in the rendered page.

SeverityMedium

CVSS6.1

Exploit probability—

Product

Showdown

PublishedJul 6, 2026

First seenJul 6, 2026

Weakness typeCWE-79Cross-site scripting (XSS)

How to fix

Sources list no fixed version or patch link for this vulnerability.

Affected products

Product	Affected versions	Fixed in
showdownnpm	v ≤ 2.1.0	—

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