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vulnerability / NVI-00009107 / Revision 6

CKEditor: Cross-site scripting (XSS) in the engine package

GitHub lists this reviewed advisory for ckeditor5, @ckeditor/ckeditor5-engine, ckeditor5, @ckeditor/ckeditor5-engine. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.

source listedactiveGHSA-rh54-vffm-5fvpCVE-2026-116688

This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.

01 / Meaning

Why it matters

Published affected context helps an owner decide what evidence to gather. This report has not examined your application.

CVSS

8.1 high

GitHub source severity; exploitability and local consequence require separate evidence.

As of · GitHub Advisory Database

EPSS

0.497%

FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.42783. Missing scores are unknown.

As of · FIRST EPSS

02 / Applicability

The affected context

Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.

ckeditor5

source listed
  • >= 45.0.0, < 47.7.4

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database

@ckeditor/ckeditor5-engine

source listed
  • >= 45.0.0, < 47.7.4

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database

ckeditor5

source listed
  • >= 48.0.0, < 48.5.1

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database

@ckeditor/ckeditor5-engine

source listed
  • >= 48.0.0, < 48.5.1

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database

ckeditor5

source listed
  • SEMVER: introduced 45.0.0; fixed 47.7.4

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database via OSV

@ckeditor/ckeditor5-engine

source listed
  • SEMVER: introduced 45.0.0; fixed 47.7.4

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database via OSV

ckeditor5

source listed
  • SEMVER: introduced 48.0.0; fixed 48.5.1

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database via OSV

@ckeditor/ckeditor5-engine

source listed
  • SEMVER: introduced 48.0.0; fixed 48.5.1

### Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the CKEditor 5 engine. This vulnerability is caused by a prototype pollution issue in the `es-toolkit` library used in the CKEditor 5 codebase. This vulnerability could lead to unauthorized JavaScript code execution when the editor processes incoming `style` attribute values. The underlying issue has been patched by the library maintainers, and the fix has been incorporated into CKEditor 5. ### Patches The problem has been recognized and patched. The fix will be available in version `48.5.1` (and above) and `47.7.4` (LTS). ### For more information Email us at security@cksource.com if you have any questions or comments about this advisory.

GitHub Advisory Database via OSV

03 / Response

What to do next

  1. investigate

    Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.

    Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS

  2. vendor patch

    The original advisory lists fixed boundaries 47.7.4 for ckeditor5. Confirm the publisher’s latest guidance.

    Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV

  3. vendor patch

    The original advisory lists fixed boundaries 47.7.4 for @ckeditor/ckeditor5-engine. Confirm the publisher’s latest guidance.

    Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV

  4. vendor patch

    The original advisory lists fixed boundaries 48.5.1 for ckeditor5. Confirm the publisher’s latest guidance.

    Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV

  5. vendor patch

    The original advisory lists fixed boundaries 48.5.1 for @ckeditor/ckeditor5-engine. Confirm the publisher’s latest guidance.

    Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV

A fixed release is not deployment evidence.

Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.

04 / Limits

What this report cannot establish

  • Customer inventory, deployment, reachability and exploitation have not been inspected.
  • NVD lastModified does not establish freshness of every associated CPE record.
Read the collection and interpretation limits ↗

05 / Provenance

Sources you can inspect

Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.

  1. GHSA-rh54-vffm-5fvp ↗

    GitHub Advisory Database · vendor advisory

    Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.

  2. GHSA-rh54-vffm-5fvp ↗

    GitHub Advisory Database via OSV · vendor advisory

    Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.

  3. CVE-2026-116688 ↗

    NIST National Vulnerability Database · official catalog

    Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.

  4. CVE-2026-116688 ↗

    FIRST EPSS · official catalog

    Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.

Public revision history

Only published revisions appear here. Routine fetches do not create a material-change event.

  1. Revision 6 ·

    Source facts changed; compare the preserved prior revision.

  2. Revision 5 ·

    Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.

  3. Revision 4 ·

    Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.

  4. Revision 3 ·

    Source facts changed; compare the preserved prior revision.

  5. Revision 2 ·

    Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.

  6. Revision 1 ·

    First indexed by Null; source disclosure date is shown separately.

Read the public revision data ↗

The next step is private

Bring the question into your environment.

The connected workflow is a development preview for inventory, contextual matching, owner decisions and evidence-based verification. No system-specific result is generated by this page.

See the synthetic workflow preview ↗