showdown metadata title handling allows cross-site scripting
GHSA-cr32-g25g-vxjj · CVE-2026-59711
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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.
References
- ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-59711
- WEB https://github.com/showdownjs/showdown/issues/1047
- WEB https://github.com/showdownjs/showdown/commit/184a3e4e97f90e075c4512f2c4c06dcf655e91b7
- PACKAGE https://github.com/showdownjs/showdown
- WEB https://www.vulncheck.com/advisories/showdown-cross-site-scripting-via-unescaped-metadata-title-in-completehtmldocument
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