Unsanitized URL schemes in MDEx Quill Delta output allow javascript: injection (XSS)

{
  "id": "f5b2d2eb8ef6f8a0fab61a8c1fe5243457ae25ac21315d77fb59ea81b86d065b",
  "url": "https://osv.dev/vulnerability/CVE-2026-54889",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Unsanitized URL schemes in MDEx Quill Delta output allow javascript: injection (XSS)",
    "summary": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in leandrocp mdex allows cross-site scripting via unsanitized URL schemes in Quill Delta output. 'Elixir.MDEx':to_delta/2 converts Markdown into a Quill Delta. 'Elixir.MDEx.DeltaConverter':default_convert_node/3 in lib/mdex/delta_converter.ex copies the URL of a link, wikilink, or image node directly from the parsed Markdown into the Delta \"link\" or \"image\" attribute without applying a scheme allowlist or any normalization. An attacker who controls the Markdown text can supply a javascript: URL (for example [click](javascript:alert(document.cookie))) that survives verbatim into the Delta attribute. When the Delta is rendered to HTML by a downstream renderer (such as quill-delta-to-html or the Quill client), the attribute becomes an or , and the javascript: scheme executes in the browser of anyone who views the rendered content. The link and wikilink cases are the strongest vectors because javascript: in an href executes on click; the image case is lower impact because javascript: in generally does not execute in modern browsers. This issue affects mdex: from 0.8.3 before 0.13.2.",
    "evidence": "osv:CVE-2026-54889",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-54889",
      "aliases": [
        "CVE-2026-54889",
        "EEF-CVE-2026-54889",
        "GHSA-4383-7xfp-gpph"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/leandrocp/mdex",
              "type": "GIT",
              "events": [
                {
                  "introduced": "9852db2456fdc9d856eb636603a7f608e22e3793"
                },
                {
                  "fixed": "2817147f5b87ce7186aa604c9ee72499485b8f2f"
                },
                {
                  "introduced": "a1e2980f3fba07358d0d3d1a76ae23c9b5639f3f"
                },
                {
                  "fixed": "c05684d9e78fc879d71ad39f2f5827b124cb5881"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "9852db2456fdc9d856eb636603a7f608e22e3793"
                      },
                      {
                        "fixed": "2817147f5b87ce7186aa604c9ee72499485b8f2f"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0.8.3"
                      },
                      {
                        "fixed": "0.13.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "2817147f5b87ce7186aa604c9ee72499485b8f2f"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.13.1",
            "v0.13.0",
            "v0.12.5",
            "v0.12.4",
            "v0.12.3",
            "v0.12.2",
            "v0.12.1",
            "v0.12.0",
            "v0.11.7",
            "v0.11.6",
            "v0.11.5",
            "v0.11.4",
            "v0.11.3",
            "v0.11.2",
            "v0.11.1",
            "v0.11.0",
            "v0.10.0",
            "v0.9.4",
            "v0.9.3",
            "v0.9.2",
            "v0.9.1",
            "v0.9.0",
            "v0.8.6",
            "v0.8.5",
            "v0.8.4",
            "v0.8.3"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54889.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.943726155Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-54889.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-54889",
        "https://repo.hex.pm",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54889.json",
        "https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-54889",
        "https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f",
        "https://github.com/leandrocp/mdex"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-79"
        ],
        "cna_assigner": "EEF",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54889.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-54889",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 498164,
  "published_at": "2026-06-29T19:10:49.841+00:00"
}