{"id":"CVE-2026-59711","summary":"showdown - Cross-Site Scripting via Unescaped Metadata Title in completeHTMLDocument","details":"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.","modified":"2026-07-09T03:51:27.422451163Z","published":"2026-07-06T21:00:38.491Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-79"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59711.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59711.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59711"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/showdown-cross-site-scripting-via-unescaped-metadata-title-in-completehtmldocument"},{"type":"REPORT","url":"https://github.com/showdownjs/showdown/issues/1047"},{"type":"PACKAGE","url":"https://github.com/showdownjs/showdown"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/showdownjs/showdown","events":[{"introduced":"0"},{"last_affected":"9958ba5cfaf01c93ea9e1a48650fb3074eff98ce"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"last_affected":"2.1.0"}],"source":"AFFECTED_FIELD"}}],"versions":["2.1.0","2.0.4","2.0.3","2.0.2","2.0.1","2.0.0","2.0.0-alpha","1.9.1","1.9.0","1.8.7","1.8.6","1.8.5","1.8.4","1.8.3","1.8.2","1.8.1","1.8.0","1.7.6","1.7.5","1.7.4","1.7.3","1.7.2","1.7.1","1.7.0","1.6.4","1.6.3","1.6.2","1.6.1","1.6.0","1.5.5","1.5.4","1.5.3","1.5.2","1.5.1","1.5.0","1.4.4","1.4.3","1.4.2","1.4.0","1.3.0","1.2.2","1.2.1","1.2.0","1.1.0","1.0.2","1.0.1","1.0.0","0.5.1","1.0.0-alpha.2","1.0.0-alpha1","0.5.0","0.4.0","v0.3.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-59711.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"}]}