showdown - Stored XSS via Unescaped Table Header ID Attribute Injection

{
  "id": "e3a2631f95cebeba453345858440e14d170bb5175f26c1681ce84868788e6924",
  "url": "https://osv.dev/vulnerability/CVE-2026-59710",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "showdown - Stored XSS via Unescaped Table Header ID Attribute Injection",
    "summary": "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.",
    "evidence": "osv:CVE-2026-59710",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-59710",
      "aliases": [
        "CVE-2026-59710",
        "GHSA-22g5-r2x5-97cx"
      ],
      "metrics": [
        {
          "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/showdownjs/showdown",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "e5cab1e9a5dcea2bb3cbf888863fa7e65ab37edf"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "2.1.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "e5cab1e9a5dcea2bb3cbf888863fa7e65ab37edf"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.0.0-rc2",
            "3.0.0-rc1",
            "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-2026-59710.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:32.850162540Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59710.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-59710",
        "https://www.vulncheck.com/advisories/showdown-stored-xss-via-unescaped-table-header-id-attribute-injection",
        "https://github.com/showdownjs/showdown/issues/1046",
        "https://github.com/showdownjs/showdown/commit/e5cab1e9a5dcea2bb3cbf888863fa7e65ab37edf",
        "https://github.com/showdownjs/showdown"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-79"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59710.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-59710",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 500031,
  "published_at": "2026-07-06T21:15:45.9+00:00"
}