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Medium, CVSS 6.9amended

Cross-site scripting (XSS) in the CKEditor 5 real-time collaboration package

CVE-2025-25299GHSA-j3mm-wmfm-mwvh

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@ckeditor/ckeditor5-real-time-collaboration 44.2.1; ckeditor5-premium-features 44.2.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N · score source
EPSS
  • CVE-2025-25299: 0.60% estimated exploitation activity in the next 30 days; percentile 48.92 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact During a recent internal audit, we identified a Cross-Site Scripting (XSS) vulnerability in the CKEditor 5 real-time collaboration package. This vulnerability can lead to unauthorized JavaScript code execution and affects user markers, which represent users' positions within the document. This vulnerability affects only installations with Real-time collaborative editing enabled.

Patches The problem has been recognized and patched. The fix will be available in version 44.2.1 (and above).

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

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  2. Revision 1 · created ·

    Published from osv record GHSA-j3mm-wmfm-mwvh

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2025-25299

Advisory: Cross-site scripting (XSS) in the CKEditor 5 real-time collaboration package
IDs: CVE-2025-25299, GHSA-j3mm-wmfm-mwvh
Record: https://patchnext.com/advisories/cve-2025-25299 (revision 2, source checked 24 Oct 2026, 22:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @ckeditor/ckeditor5-real-time-collaboration 44.2.1; ckeditor5-premium-features 44.2.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @ckeditor/ckeditor5-real-time-collaboration: affected >= 41.3.0, < 44.2.1; fixed in 44.2.1
- npm ckeditor5-premium-features: affected >= 42.0.0, < 44.2.1; fixed in 44.2.1

## Suggested inspection (read-only)
- `npm ls @ckeditor/ckeditor5-real-time-collaboration --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls ckeditor5-premium-features --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @ckeditor/ckeditor5-real-time-collaboration, ckeditor5-premium-features.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-j3mm-wmfm-mwvh (OSV record GHSA-j3mm-wmfm-mwvh lists affected ranges: npm @ckeditor/ckeditor5-real-time-collaboration >=41.3.0 =42.0.0 <44.2.1 (fixed))

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