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HighVulnerabilityCVE-2026-116688updated 27 Oct 2026, 21:06 UTC

CKEditor 5 can run attacker-supplied scripts in the browser via crafted content

A specially crafted piece of text pasted or loaded into the CKEditor rich-text box can make the browser run hidden code. That code can act as the logged-in user on the page.

Fix availableOfficial, 2 sources
SeverityHighCVSS 8.1 of 10
Being exploited?UnclearNo reports either way yet
Fix available?Yesckeditor5 and @ckeditor/ckeditor5-engine 47.7.4 (LTS) and 48.5.1 or later · since 27 Oct 2026
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Attacker crafts contentMalicious style attribute value is prepared
  2. 2Content enters editorPasted or loaded into CKEditor 5
  3. 3Engine processes stylesVulnerable es-toolkit prototype pollution triggers
  4. 4Script runs in browserUnauthorized JavaScript executes for the viewer
  5. ResultAttacker runs JavaScript in user browsers

What happened

A prototype pollution flaw in the es-toolkit library used by the CKEditor 5 engine is reachable while the editor processes incoming style attribute values, enabling cross-site scripting (XSS).

Why it is dangerous: Anyone who can get crafted content into a page using the affected editor can run JavaScript in other users' browsers, potentially stealing sessions or data.

Are you affected?

You are affected if your application uses ckeditor5 or @ckeditor/ckeditor5-engine versions 45.0.0 up to 47.7.4, or 48.0.0 up to 48.5.1.

Package / productAffected versionsFixed in
ckeditor5 · npm>= 45.0.0, < 47.7.447.7.4
@ckeditor/ckeditor5-engine · npm>= 45.0.0, < 47.7.447.7.4
ckeditor5 · npm>= 48.0.0, < 48.5.148.5.1
@ckeditor/ckeditor5-engine · npm>= 48.0.0, < 48.5.148.5.1

What to do

  1. Update ckeditor5 and @ckeditor/ckeditor5-engine to 47.7.4 (LTS) or 48.5.1 or later
  2. Rebuild and redeploy your application so the fixed editor code is served to users
  3. Review stored editor content for suspicious style attributes if the editor was used with untrusted input

Timeline

  1. 27 Oct 2026, 20:17 UTC
    Publicly disclosed
  2. 27 Oct 2026, 20:17 UTC
    Reported by NVD · NVD
  3. 27 Oct 2026, 20:21 UTC
    Picked up by Zero Radar
  4. 27 Oct 2026, 21:06 UTC
    GitHub Advisory reported on it · GitHub Advisory
  5. 27 Oct 2026, 21:06 UTC
    Fixed version published: ckeditor5 47.7.4, @ckeditor/ckeditor5-engine 47.7.4, ckeditor5 48.5.1 · GitHub Advisory

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-116688 · GHSA-rh54-vffm-5fvp
CVSS
8.1 / 10
EPSS
0.5% chance of exploitation within 30 days
Disclosed
27 Oct 2026, 20:17 UTC
On Zero Radar
27 Oct 2026, 20:21 UTC (4 min after disclosure)
Last change
27 Oct 2026, 21:06 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

CKEditor 5 can run attacker-supplied scripts in the browser via crafted content · Zero Radar