CVE-2026-59711 Details
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.
A cross-site scripting vulnerability has been identified in Showdown, a JavaScript Markdown to HTML converter, in versions through 2.1.0. The issue arises when the 'completeHTMLDocument' option is enabled, allowing unescaped less-than and greater-than characters in Markdown frontmatter metadata to be injected into HTML title tags. This exploitation enables attackers to break out of the title context and execute malicious scripts on the rendered page.
Users can update to Showdown version 3.0.0 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jul 6, 2026CISA-ADP
Assessed Jul 7, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/showdownjs/showdown/issues/1047 | CISA-ADP | ExploitIssue TrackingTechnical DescriptionVendor |
| https://github.com/showdownjs/showdown | [email protected] | ProductSource CodeVendor |
| https://github.com/showdownjs/showdown/issues/1047 | [email protected] | ExploitIssue TrackingTechnical DescriptionVendor |
| https://www.vulncheck.com/advisories/showdown-cross-site-scripting-via-unescaped-metadata-title-in-completehtmldocument | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| showdownjs showdown | <= 2.1.0 (semver) |
CPE
Remediation
| |
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 7, 2026 | CVE Modified | CISA-ADP |
| Jul 6, 2026 | New CVE Received | [email protected] |