Concrete CMS below 9.5.3 is vulnerable to Stored XSS via unsanitized inline block custom style values

{
  "id": "68860d225b4913c53a49c5312d68dc100426f0abdd05e64a70cbc285c01bdef5",
  "url": "https://osv.dev/vulnerability/CVE-2026-18119",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Concrete CMS below 9.5.3 is vulnerable to Stored XSS via unsanitized inline block custom style values",
    "summary": "Concrete CMS below 9.5.3 did not sanitize custom style values in the Block Design dialog before writing them into page CSS via a DOM sink, permitting stored cross-site scripting. An editor-level user could execute script in an administrator's session and escalate privileges. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.0 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Nguyen Manh Thuan for reporting.",
    "evidence": "osv:CVE-2026-18119",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-18119",
      "aliases": [
        "CVE-2026-18119"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/concretecms/concretecms",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "9379c29cb26a1054208b37507b6869811aa75a32"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "5.0.0"
                      },
                      {
                        "last_affected": "9.5.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "cpe": "cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "9.5.3"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "9.5.2",
            "9.5.1",
            "9.5.0",
            "9.5.0RC2",
            "9.5.0RC1",
            "9.4.4",
            "9.4.3",
            "9.4.2",
            "9.4.1",
            "9.4.0",
            "9.4.0RC2",
            "9.4.0RC1",
            "9.3.7",
            "9.3.6",
            "9.3.5",
            "9.3.0",
            "9.3.4",
            "9.3.3",
            "9.3.2",
            "9.3.1",
            "8.4.1",
            "8.3.1",
            "8.2.1",
            "8.2.0",
            "8.2.0RC2",
            "8.1.0",
            "5.7.5.7",
            "5.7.5.6",
            "5.7.5.5",
            "5.7.5.2",
            "5.7.4.1",
            "5.7.3.1",
            "5.7.3",
            "5.7.2.1",
            "5.7.2",
            "5.7.0.4",
            "5.7.1",
            "5.7.0.3",
            "5.7.0.1",
            "5.7.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-18119.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.696557684Z",
      "provider": "osv",
      "references": [
        "https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/18xxx/CVE-2026-18119.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-18119",
        "https://github.com/concretecms/concretecms"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-79"
        ],
        "cna_assigner": "ConcreteCMS",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/18xxx/CVE-2026-18119.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-18119",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519427,
  "published_at": "2026-09-14T19:54:11.734+00:00"
}