CVE-2026-59711: Showdown

Medium severity, CVSS 6.1. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Showdown Showdown: up to and including 2.1.0

Published 2026-07-06. Last modified 2026-07-07.