CVE-2023-28439: CKEditor4 is an open source what-you-see-is-what-you-get HTML editor. A cross-site scripting vulnerability has been discovered affecting Iframe Dialog...

Description

CKEditor4 is an open source what-you-see-is-what-you-get HTML editor. A cross-site scripting vulnerability has been discovered affecting Iframe Dialog and Media Embed packages. The vulnerability may trigger a JavaScript code after fulfilling special conditions: using one of the affected packages on a web page with missing proper Content Security Policy configuration; initializing the editor on an element and using an element other than `<textarea>` as a base; and destroying the editor instance. This vulnerability might affect a small percentage of integrators that depend on dynamic editor initialization/destroy mechanism. A fix is available in CKEditor4 version 4.21.0. In some rare cases, a security fix may be considered a breaking change. Starting from version 4.21.0, the Iframe Dialog plugin applies the `sandbox` attribute by default, which restricts JavaScript code execution in the iframe element. To change this behavior, configure the `config.iframe_attributes` option. Also starting from version 4.21.0, the Media Embed plugin regenerates the entire content of the embed widget by default. To change this behavior, configure the `config.embed_keepOriginalContent` option. Those who choose to enable either of the more permissive options or who cannot upgrade to a patched version should properly configure Content Security Policy to avoid any potential security issues that may arise from embedding iframe elements on their web page.

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

0.73%

49.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Ckeditor	Ckeditor	>= 4.0, < 4.21.0
Fedoraproject	Fedora	37
Fedoraproject	Fedora	38
Fedoraproject	Fedora	39

References

https://ckeditor.com/cke4/addon/embedProduct
https://ckeditor.com/cke4/addon/iframeProduct
https://github.com/ckeditor/ckeditor4/security/advisories/GHSA-vh5c-xwqv-cv9gVendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GWKG2VCPJNETVCDTXU4X6FQ2PO6XCNGN/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/L4ODGOW6PYVOXHQSMWJBOCE6DXWAI33W/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VCYKD3JZWWA3ESOZG4PHJJEXT4EYIUIQ/Mailing List
https://ckeditor.com/cke4/addon/embedProduct
https://ckeditor.com/cke4/addon/iframeProduct
https://github.com/ckeditor/ckeditor4/security/advisories/GHSA-vh5c-xwqv-cv9gVendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GWKG2VCPJNETVCDTXU4X6FQ2PO6XCNGN/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/L4ODGOW6PYVOXHQSMWJBOCE6DXWAI33W/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VCYKD3JZWWA3ESOZG4PHJJEXT4EYIUIQ/Mailing List

Timeline

Published: Mar 22, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-28439?

CKEditor4 is an open source what-you-see-is-what-you-get HTML editor. A cross-site scripting vulnerability has been discovered affecting Iframe Dialog and Media Embed packages. The vulnerability may trigger a JavaScript code after fulfilling special conditions: using one of the affected packages on a web page with missing proper Content Security Policy configuration; initializing the editor on an element and using an element other than `<textarea>` as a base; and destroying the editor instance. This vulnerability might affect a small percentage of integrators that depend on dynamic editor initialization/destroy mechanism. A fix is available in CKEditor4 version 4.21.0. In some rare cases, a security fix may be considered a breaking change. Starting from version 4.21.0, the Iframe Dialog plugin applies the `sandbox` attribute by default, which restricts JavaScript code execution in the iframe element. To change this behavior, configure the `config.iframe_attributes` option. Also starting from version 4.21.0, the Media Embed plugin regenerates the entire content of the embed widget by default. To change this behavior, configure the `config.embed_keepOriginalContent` option. Those who choose to enable either of the more permissive options or who cannot upgrade to a patched version should properly configure Content Security Policy to avoid any potential security issues that may arise from embedding iframe elements on their web page.

How severe is CVE-2023-28439?

CVE-2023-28439 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.73% probability of exploitation in the next 30 days.

How do I fix CVE-2023-28439?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.