Security advisory

{
  "id": "c9d11136757b406c9fcb44f3b5e3936d29841278e93e43cf6610ecf99471c271",
  "url": "https://osv.dev/vulnerability/CVE-2021-27279",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-27279",
    "summary": "MyBB before 1.8.25 allows stored XSS via nested [email] tags with MyCode (aka BBCode).",
    "evidence": "osv:CVE-2021-27279",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2021-27279",
      "aliases": [
        "CVE-2021-27279",
        "GHSA-6483-hcpp-p75w"
      ],
      "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/mybb/mybb",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "cb781b49116bf5c4d8deca3e17498122b701677a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "fixed": "cb781b49116bf5c4d8deca3e17498122b701677a"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "mybb_1824",
            "mybb_1823_build",
            "mybb_1823",
            "mybb_1822",
            "mybb_1822_build",
            "mybb_1821pl1",
            "mybb_1821",
            "mybb_1821_build",
            "mybb_1817_build",
            "mybb_1817",
            "mybb_1820",
            "mybb_1820_build",
            "mybb_1820-rc",
            "mybb_1819",
            "mybb_1818",
            "mybb_1819_build",
            "mybb_1818_build",
            "mybb_1816",
            "mybb_1816_build",
            "mybb_1815",
            "mybb_1815_build",
            "mybb_1814",
            "mybb_1813",
            "mybb_1812",
            "mybb_1811",
            "mybb_1810",
            "mybb_1809",
            "mybb_1808",
            "mybb_1807",
            "mybb_1806",
            "mybb_1805",
            "mybb_1804",
            "mybb_1800",
            "mybb_1801"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-27279.json"
          }
        }
      ],
      "modified": "2026-10-20T10:54:35.200349794Z",
      "provider": "osv",
      "references": [
        "https://mybb.com/versions/1.8.25/",
        "https://github.com/mybb/mybb/commit/cb781b49116bf5c4d8deca3e17498122b701677a",
        "https://github.com/mybb/mybb/security/advisories/GHSA-6483-hcpp-p75w"
      ],
      "provider_metadata": {
        "unresolved_ranges": [
          {
            "cpes": [
              "cpe:2.3:a:mybb:mybb:*:*:*:*:*:*:*:*"
            ],
            "vendor_product": "mybb:mybb",
            "extracted_events": [
              {
                "range": [
                  {
                    "fixed": "1.8.25"
                  }
                ],
                "source": "CPE_RANGE"
              }
            ]
          },
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "fixed": "1.8.25"
                  }
                ],
                "source": "DESCRIPTION"
              }
            ]
          }
        ]
      }
    },
    "related_cves": [
      {
        "value": "CVE-2021-27279",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 385668,
  "published_at": "2021-02-22T20:15:13.243+00:00"
}