GHSA-JRQM-VMQC-GM93

Vulnerability from github – Published: 2026-03-04 18:49 – Updated: 2026-03-19 18:45
VLAI?
Summary
CKEditor 5 has Cross-site Scripting (XSS) in the HTML Support package
Details

Impact

A Cross-Site Scripting (XSS) vulnerability has been discovered in the General HTML Support feature. This vulnerability could be triggered by inserting specially crafted markup, leading to unauthorized JavaScript code execution, if the editor instance used an unsafe General HTML Support configuration.

This vulnerability affects only installations where the editor configuration meets the following criteria:

Patches

The problem has been recognized and patched. The fix will be available in version 47.6.0 (and above).

Workarounds

CKEditor 5 recommends configuring General HTML Support securely to ensure that unsafe content is not accepted. Please refer to the Security section for detailed guidance.

Credits

CKEditor 5 would like to thank: - Emilio Kevin - Jeongwoo Lee, Younsoung Kim, Minseok Kim and Jinyeong Kim from ENKI Whitehat

for responsibly reporting this vulnerability.

For more information

Email us at security@cksource.com if you have any questions or comments about this advisory.

Severity ?
6.4 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@ckeditor/ckeditor5-html-support"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "29.0.0"
            },
            {
              "fixed": "47.6.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "ckeditor5"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "29.0.0"
            },
            {
              "fixed": "47.6.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-28343"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-04T18:49:32Z",
    "nvd_published_at": "2026-03-05T20:16:16Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\nA Cross-Site Scripting (XSS) vulnerability has been discovered in the General HTML Support feature. This vulnerability could be triggered by inserting specially crafted markup, leading to unauthorized JavaScript code execution, if the editor instance used an unsafe General HTML Support configuration.\n\nThis vulnerability affects only installations where the editor configuration meets the following criteria:\n\n* [General HTML Support](https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html) is enabled,\n* General HTML Support configuration allows inserting unsafe markup (see [Security](https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html#security) section to learn more).\n\n### Patches\nThe problem has been recognized and patched. The fix will be available in version 47.6.0 (and above).\n\n### Workarounds\nCKEditor 5 recommends configuring General HTML Support securely to ensure that unsafe content is not accepted. Please refer to the [Security](https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html#security) section for detailed guidance.\n\n### Credits\nCKEditor 5 would like to thank: \n- Emilio Kevin\n- Jeongwoo Lee, Younsoung Kim, Minseok Kim and Jinyeong Kim from ENKI Whitehat\n\nfor responsibly reporting this vulnerability.\n\n### For more information\nEmail us at [security@cksource.com](mailto:security@cksource.com) if you have any questions or comments about this advisory.",
  "id": "GHSA-jrqm-vmqc-gm93",
  "modified": "2026-03-19T18:45:07Z",
  "published": "2026-03-04T18:49:32Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-jrqm-vmqc-gm93"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-28343"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ckeditor/ckeditor5"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ckeditor/ckeditor5/releases/tag/v29.0.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ckeditor/ckeditor5/releases/tag/v47.6.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "CKEditor 5 has Cross-site Scripting (XSS) in the HTML Support package"
}


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Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.