Medium severity · published Jul 6, 2026
CVE-2026-59710
showdown - Stored XSS via Unescaped Table Header ID Attribute Injection
6.1
CVSS
0.3%
EPSS
No
On KEV
Description
showdown contains a stored cross-site scripting vulnerability in the parseHeaders function of src/subParsers/makehtml/tables.js that fails to properly escape table header ID attributes. Attackers can inject arbitrary HTML and script-executing SVG elements through double-quote characters in markdown table headers, achieving stored XSS when untrusted markdown is rendered with the default github flavor configuration.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 27% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SH
showdown · showdown
through 2.1.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59710
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-59710
github.com
https://github.com/showdownjs/showdown
github.com
https://github.com/showdownjs/showdown/commit/e5cab1e9a5dcea2bb3cbf888863fa7e65ab37edf
github.com
https://github.com/showdownjs/showdown/issues/1046
www.vulncheck.com
https://www.vulncheck.com/advisories/showdown-stored-xss-via-unescaped-table-header-id-attribute-injection
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CVE-2026-59711
showdown - Cross-Site Scripting via Unescaped Metadata Title in completeHTMLDocument