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6.4
CKEditor 5 allows malicious code to run on websites
CVE-2026-28343
GHSA-jrqm-vmqc-gm93
Summary
CKEditor 5 has a security flaw that could allow hackers to inject malicious code on websites using the editor, potentially stealing user data or causing other harm. This issue only affects websites that use CKEditor 5 and have a specific configuration setting enabled. To stay safe, update to the latest version (47.6.0 or higher) or configure the editor to block malicious code as recommended by the developers.
What to do
- Update ckeditor ckeditor5-html-support to version 47.6.0.
- Update ckeditor ckeditor5 to version 47.6.0.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| ckeditor | ckeditor5-html-support | <= 47.6.0 | 47.6.0 |
| ckeditor | ckeditor5 | <= 47.6.0 | 47.6.0 |
Original title
CKEditor 5 has Cross-site Scripting (XSS) in the HTML Support package
Original description
### 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:
* [General HTML Support](https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html) is enabled,
* 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).
### 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](https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html#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 [[email protected]](mailto:[email protected]) if you have any questions or comments about this advisory.
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:
* [General HTML Support](https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html) is enabled,
* 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).
### 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](https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html#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 [[email protected]](mailto:[email protected]) if you have any questions or comments about this advisory.
nvd CVSS3.1
6.4
Vulnerability type
CWE-79
Cross-site Scripting (XSS)
Published: 4 Mar 2026 · Updated: 13 Mar 2026 · First seen: 6 Mar 2026