showdown metadata title handling allows cross-site scripting
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 software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | showdown | <= 2.1.0 | no fix |
References
- https://nvd.nist.gov/vuln/detail/CVE-2026-59711
- https://github.com/showdownjs/showdown/issues/1047
- https://github.com/showdownjs/showdown/commit/184a3e4e97f90e075c4512f2c4c06dcf655e91b7
- https://github.com/showdownjs/showdown
- https://www.vulncheck.com/advisories/showdown-cross-site-scripting-via-unescaped-metadata-title-in-completehtmldocument
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- Weakness (CWE)
CWE-79- Platform
- npm
- Package
showdown- Disclosed
- 06.07.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-cr32-g25g-vxjj - CC BY 4.0
Vulnerability history: showdown
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 4
- First → latest
- 09.2020 07.2026
- Without a fix
- 3
- Exploited in attacks
- 0
Severity breakdown
- Medium 3
- Low 1
Disclosures per year
- 2020: 1
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 1
- 2025: 0
- 2026: 2
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