Security advisory

{
  "id": "0a85c642c3c73dae727f3c2e154fea90e90d324c61693be21eeff5324aff6ebb",
  "url": "https://osv.dev/vulnerability/CVE-2021-47857",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-47857",
    "summary": "Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when users view the event.",
    "evidence": "osv:CVE-2021-47857",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2021-47857",
      "aliases": [
        "BIT-moodle-2021-47857",
        "CVE-2021-47857"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/moodle/moodle",
              "type": "GIT",
              "events": [
                {
                  "introduced": "ef7fcf42612ffcc289f804cf0b83a76631f83f70"
                },
                {
                  "last_affected": "ef7fcf42612ffcc289f804cf0b83a76631f83f70"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:moodle:moodle:3.10.3:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "3.10.3"
                      },
                      {
                        "last_affected": "3.10.3"
                      }
                    ],
                    "source": "CPE_STRING"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.10.3",
            "v3.10.3"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47857.json"
          }
        }
      ],
      "modified": "2026-10-24T10:30:50.045219956Z",
      "provider": "osv",
      "references": [
        "https://moodle.org/",
        "https://www.vulncheck.com/advisories/moodle-label-persistent-cross-site-scripting",
        "https://www.exploit-db.com/exploits/49714"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2021-47857",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 437133,
  "published_at": "2026-01-21T18:16:16.567+00:00"
}