XSS in Showdown
CVE-2026-59710
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (25.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Showdown — versions 0
Weakness classification (CWE)
References
- github.com/showdownjs/showdown/issues/1046 (issue-tracking)
- github.com/showdownjs/showdown (product)
- github.com/showdownjs/showdown/commit/e5cab1e9a5dcea2bb3cbf888863fa7e65ab37edf (patch)
- www.vulncheck.com/advisories/showdown-stored-xss-via-unescaped-table-header-id-… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-59710?
- CVE-2026-59710 is a medium-severity vulnerability in Showdown, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-07-06.
- How severe is CVE-2026-59710?
- Medium severity. CVSS v3 base score is 6.1 out of 10.