EmbedVideo Extension : Stored XSS via unsanitized class passed to template

{
  "id": "39334c89e00aa3ecddab04f801f5c40e25eac89e45746960532bb2ec2508be62",
  "url": "https://osv.dev/vulnerability/CVE-2026-55691",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "EmbedVideo Extension : Stored XSS via unsanitized class passed to template",
    "summary": "The EmbedVideo Extension is a MediaWiki extension which adds a parser function called #ev and various parser tags for embedding video clips from various video sharing services. Prior to 4.1.0, EmbedHtmlFormatter::toHtml in includes/EmbedService/EmbedHtmlFormatter.php passes the user-supplied class value directly to sprintf while constructing a figure element. A quote in the class value can terminate the class attribute and inject arbitrary HTML attributes or markup into the rendered page. A user able to edit a wiki page can store JavaScript that executes for visitors who render the affected content. This issue is fixed in version 4.1.0.",
    "evidence": "osv:CVE-2026-55691",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-55691",
      "aliases": [
        "CVE-2026-55691",
        "GHSA-7h5p-637f-jfr7"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/starcitizenwiki/mediawiki-extensions-embedvideo",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "6982ef6e10a8327a6ecc97eb036f4eb531a6f830"
                },
                {
                  "fixed": "370156335b325bb81d14d89edf0a1f2643d50a84"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.1.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "370156335b325bb81d14d89edf0a1f2643d50a84"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "6982ef6e10a8327a6ecc97eb036f4eb531a6f830"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v4.1.0"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v4.0.0",
            "v3.1.0",
            "v3.0.0",
            "v2.9.0",
            "v2.8.0",
            "v2.7.4",
            "v2.7.3",
            "v2.7.2",
            "2.7.2",
            "v2.7.1",
            "v2.7.0",
            "v2.6.1",
            "v2.6.0",
            "v2.5.2",
            "v2.5.0",
            "v2.4.1",
            "v2.4.0",
            "v2.3.3",
            "v2.3.2",
            "v2.3.1",
            "v2.3.0",
            "v2.2.9",
            "v2.2.8",
            "v2.2.7",
            "v2.2.6",
            "v2.2.5",
            "v2.2.4",
            "v2.2.3",
            "v2.2.2",
            "v2.2.1",
            "v2.2.0",
            "v2.1.8",
            "v2.1.7",
            "v2.1.6",
            "v2.1.5",
            "v2.1.4",
            "v2.1.3",
            "v2.1.2",
            "v2.1",
            "v2.1alpha1",
            "v2.0",
            "v2.0beta3",
            "v2.0beta2",
            "v2.0beta1",
            "v1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55691.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.149014924Z",
      "provider": "osv",
      "references": [
        "https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/releases/tag/v4.1.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55691.json",
        "https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/security/advisories/GHSA-7h5p-637f-jfr7",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-55691",
        "https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/commit/370156335b325bb81d14d89edf0a1f2643d50a84"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-79"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55691.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-55691",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518436,
  "published_at": "2026-09-15T16:34:59.998+00:00"
}