CVE-2026-59711CWE-79

showdown - Cross-Site Scripting via Unescaped Metadata Title in completeHTMLDocument

Medium · published July 6, 2026

CVSS v4.0
5.3
EPSS
0%
Percentile
24.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
5.3 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
EPSS
0.00327 · 24.6th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-07-06T21:00Z
EPSS history
Timeline
  • 06 JUL 21:00Z
    showdown - Cross-Site Scripting via Unescaped Metadata Title in completeHTMLDocument
    cvelistv5