Medium

AVideo Vulnerable to Stored XSS via Markdown `javascript:` URI Bypasses ParsedownSafeWithLinks Sanitization

Type: advisorySources: OSV

WWBN AVideo is an open source video platform. In versions up to and including 26.0, the fix for CVE-2026-27568 (GHSA-rcqw-6466-3mv7) introduced a custom `ParsedownSafeWithLinks` class that sanitizes raw HTML `` and `` tags in comments, but explicitly disables Parsedown's `safeMode`. This creates a bypass: markdown link syntax `[text](javascript:alert(1))` is processed by Parsedown's `inlineLink()` method, which does not go through the custom `sanitizeATag()` sanitization (that only handles raw HTML tags). With `safeMode` disabled, Parsedown's built-in `javascript:` URI filtering (`sanitiseElement()`/`filterUnsafeUrlInAttribute()`) is also inactive. An attacker can inject stored XSS via comment markdown links. Commit 3ae02fa240939dbefc5949d64f05790fd25d728d contains a patch.

Products: Not specified
Affected versions: Not specified
Fixed versions: Not specified
CVEs: CVE-2026-33500
Confirmed fixed CVEs: Not specified
Updated in this feed: 4 Nov 2026, 23:21 UTC · Revision 1

Source evidence

AVideo Vulnerable to Stored XSS via Markdown `javascript:` URI Bypasses ParsedownSafeWithLinks Sanitization

core-osv · Original source

Published 23 Mar 2026, 16:24 UTC

osv:CVE-2026-33500

Complete source record

{
  "id": "0dff3816a06ac8d42518f4c38ceb20c0f24c3bb677a80a38a76c167406ab9ae1",
  "url": "https://osv.dev/vulnerability/CVE-2026-33500",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "AVideo Vulnerable to Stored XSS via Markdown `javascript:` URI Bypasses ParsedownSafeWithLinks Sanitization",
    "summary": "WWBN AVideo is an open source video platform. In versions up to and including 26.0, the fix for CVE-2026-27568 (GHSA-rcqw-6466-3mv7) introduced a custom `ParsedownSafeWithLinks` class that sanitizes raw HTML `` and `` tags in comments, but explicitly disables Parsedown's `safeMode`. This creates a bypass: markdown link syntax `[text](javascript:alert(1))` is processed by Parsedown's `inlineLink()` method, which does not go through the custom `sanitizeATag()` sanitization (that only handles raw HTML tags). With `safeMode` disabled, Parsedown's built-in `javascript:` URI filtering (`sanitiseElement()`/`filterUnsafeUrlInAttribute()`) is also inactive. An attacker can inject stored XSS via comment markdown links. Commit 3ae02fa240939dbefc5949d64f05790fd25d728d contains a patch.",
    "evidence": "osv:CVE-2026-33500",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-33500",
      "aliases": [
        "CVE-2026-33500",
        "GHSA-72h5-39r7-r26j"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/wwbn/avideo",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3ae02fa240939dbefc5949d64f05790fd25d728d"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:wwbn:avideo:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "26.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "3ae02fa240939dbefc5949d64f05790fd25d728d"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "26.0",
            "25.0",
            "24.0",
            "22.0",
            "21.0",
            "18.0",
            "14.3.1",
            "14.3",
            "12.4",
            "11.6",
            "11.5",
            "11.1.1",
            "11.1",
            "11",
            "10.8",
            "8.9.1",
            "8.9",
            "8.7",
            "8.6",
            "8.5",
            "8.1",
            "7.8",
            "7.7",
            "7.6",
            "7.4",
            "7.3",
            "7.2",
            "4.0",
            "3.4",
            "2.7",
            "2.2"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33500.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:40.570486704Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33500.json",
        "https://github.com/WWBN/AVideo/security/advisories/GHSA-72h5-39r7-r26j",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-33500",
        "https://github.com/WWBN/AVideo/commit/3ae02fa240939dbefc5949d64f05790fd25d728d"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-79"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33500.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-33500",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 507964,
  "published_at": "2026-03-23T16:24:52.892+00:00"
}