CVE-2026-59167

SunEditor is a lightweight and powerful WYSIWYG editor in vanilla JavaScript with no dependencies. Prior to 2.47.11, the sanitizer in src/lib/core.js does not consistently reject namespaced or custom HTML elements, allowing event-handler attributes to remain on crafted elements. When an application renders attacker-controlled editor content and a user interacts with the element, the retained handler can execute script in the application's browser origin, enabling stored cross-site scripting, data exposure, or unauthorized browser-context actions. This issue is fixed in version 2.47.11.

SunEditor is a lightweight and powerful WYSIWYG editor in vanilla JavaScript with no dependencies. Prior to 2.47.11, the sanitizer in src/lib/core.js does not consistently reject namespaced or custom HTML elements, allowing event-handler attributes to remain on crafted elements. When an application renders attacker-controlled editor content and a user interacts with the element, the retained handler can execute script in the application's browser origin, enabling stored cross-site scripting, data exposure, or unauthorized browser-context actions. This issue is fixed in version 2.47.11.

Summary

SUNEDITOR v2.47.10 appears to allow JavaScript execution through crafted namespaced HTML elements.

The sanitization logic does not fully remove executable event-handler attributes from certain custom/namespaced tags. As a result, an attacker may be able to inject HTML content that executes JavaScript when the rendered element is interacted with.

This behavior was observed after the changes introduced in this commit:

https://github.com/JiHong88/suneditor/commit/9ed405fb0de676e56cd0e6a13c19c103ad5948d3

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Affected Version

Confirmed vulnerable:

• SUNEDITOR =< 2.47.10

Potentially affected:

• Previous versions, if the same sanitization logic is still present

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Proof of Concept

The following payload preserves an executable event handler:

<a:b src="/x"><iframe src=javascript:alert(1)></iframe></a:b>

<p><a:b src="/x" onclick="document.body.style.background='red'">click</a:b></p>

Simplified PoC:

<a:b src="/x" onclick="console.log('XSS:',document.domain,document.cookie)">click</a:b>

<p><a:b src="/x" onmouseover="alert('XSS — '+document.domain)">📎 Click here for solutions</a:b></p>

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Steps to Reproduce

1. Open SUNEDITOR using version 2.47.10.
2. Insert the payload above into the editor.
3. Save or render the generated content.
4. Click the generated element.
5. Observe that JavaScript is executed.

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Impact

This may allow an attacker to inject arbitrary JavaScript into rendered editor content.

Depending on how SUNEDITOR is integrated into an application, this could lead to:

• Stored XSS
• DOM manipulation
• Session theft
• Credential theft
• Account takeover actions performed in the victim’s browser context

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Technical Details

The issue appears to be related to incomplete handling of namespaced/custom HTML elements such as:

<a:b>

Event-handler attributes such as onclick can remain attached to these crafted elements and execute when interacted with.

This suggests that the sanitization process may not consistently normalize and validate custom or namespaced elements before applying attribute filtering.

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Suggested Remediation

Possible mitigations include:

• Normalize DOM elements before sanitization.
• Explicitly reject or unwrap unknown/custom/namespaced tags.
• Strip all event-handler attributes from all elements, including unknown/custom elements.
• Re-validate sanitized output after browser DOM parsing.
• Add regression tests for namespaced/custom tag payloads.

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SunEditor is a lightweight and powerful WYSIWYG editor in vanilla JavaScript with no dependencies. Prior to 2.47.11, the sanitizer in src/lib/core.js does not consistently reject namespaced or custom HTML elements, allowing event-handler attributes to remain on crafted elements. When an application renders attacker-controlled editor content and a user interacts with the element, the retained handler can execute script in the application's browser origin, enabling stored cross-site scripting, data exposure, or unauthorized browser-context actions. This issue is fixed in version 2.47.11.

SunEditor is a lightweight and powerful WYSIWYG editor in vanilla JavaScript with no dependencies. Prior to 2.47.11, the sanitizer in src/lib/core.js does not consistently reject namespaced or custom HTML elements, allowing event-handler attributes to remain on crafted elements. When an application renders attacker-controlled editor content and a user interacts with the element, the retained handler can execute script in the application's browser origin, enabling stored cross-site scripting, data exposure, or unauthorized browser-context actions. This issue is fixed in version 2.47.11.

Summary

SUNEDITOR v2.47.10 appears to allow JavaScript execution through crafted namespaced HTML elements.

The sanitization logic does not fully remove executable event-handler attributes from certain custom/namespaced tags. As a result, an attacker may be able to inject HTML content that executes JavaScript when the rendered element is interacted with.

This behavior was observed after the changes introduced in this commit:

https://github.com/JiHong88/suneditor/commit/9ed405fb0de676e56cd0e6a13c19c103ad5948d3

---

Affected Version

Confirmed vulnerable:

• SUNEDITOR =< 2.47.10

Potentially affected:

• Previous versions, if the same sanitization logic is still present

---

Proof of Concept

The following payload preserves an executable event handler:

<a:b src="/x"><iframe src=javascript:alert(1)></iframe></a:b>

<p><a:b src="/x" onclick="document.body.style.background='red'">click</a:b></p>

Simplified PoC:

<a:b src="/x" onclick="console.log('XSS:',document.domain,document.cookie)">click</a:b>

<p><a:b src="/x" onmouseover="alert('XSS — '+document.domain)">📎 Click here for solutions</a:b></p>

---

Steps to Reproduce

1. Open SUNEDITOR using version 2.47.10.
2. Insert the payload above into the editor.
3. Save or render the generated content.
4. Click the generated element.
5. Observe that JavaScript is executed.

---

Impact

This may allow an attacker to inject arbitrary JavaScript into rendered editor content.

Depending on how SUNEDITOR is integrated into an application, this could lead to:

• Stored XSS
• DOM manipulation
• Session theft
• Credential theft
• Account takeover actions performed in the victim’s browser context

---

Technical Details

The issue appears to be related to incomplete handling of namespaced/custom HTML elements such as:

<a:b>

Event-handler attributes such as onclick can remain attached to these crafted elements and execute when interacted with.

This suggests that the sanitization process may not consistently normalize and validate custom or namespaced elements before applying attribute filtering.

---

Suggested Remediation

Possible mitigations include:

• Normalize DOM elements before sanitization.
• Explicitly reject or unwrap unknown/custom/namespaced tags.
• Strip all event-handler attributes from all elements, including unknown/custom elements.
• Re-validate sanitized output after browser DOM parsing.
• Add regression tests for namespaced/custom tag payloads.

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