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CVE-2026-59711

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.
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:30da61931b7cf80b0438a46f17285f7dea4291d5792bf5124c4a53d5021b1342
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cvss · 2 assertions

{"metric":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":5.3,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","userInteraction":"PASSIVE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact…

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/metrics/0/cvssV4_0

{"metric":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":6.1,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/metrics/1/cvssV3_1

Affected products and versions

1 source assertion
{"defaultStatus":"unaffected","packageURL":"pkg:npm/showdown","product":"showdown","vendor":"showdown","versions":[{"lessThanOrEqual":"2.1.0","status":"affected","version":"0","versionType":"semver"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/affected/0

Provider-owned CVSS observations

2 source assertions
{"metric":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":5.3,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","userInteraction":"PASSIVE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact…
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/metrics/0/cvssV4_0
{"metric":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":6.1,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/metrics/1/cvssV3_1

CWE assertions

1 source assertion
{"cweId":"CWE-79","description":"Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/problemTypes/0/descriptions/0

Source references

4 source assertions
{"name":"Product","tags":["product"],"url":"https://github.com/showdownjs/showdown"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/references/1
{"name":"GitHub Issue","tags":["issue-tracking"],"url":"https://github.com/showdownjs/showdown/issues/1047"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/references/0
{"tags":["exploit"],"url":"https://github.com/showdownjs/showdown/issues/1047"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/adp/0/references/0
{"tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/showdown-cross-site-scripting-via-unescaped-metadata-title-in-completehtmldocument"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:d6f4a25dc0182af7999249733d56b8a02114d90d52f7a8e0140d0cb020a4e895 · sha256:359c2eb534c43449… · /containers/cna/references/2

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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