CVE-2026-25581: SCEditor WYSIWYG XSS Vulnerability

CVE-2026-25581 Overview

CVE-2026-25581 is a Cross-Site Scripting (XSS) vulnerability in SCEditor, a lightweight WYSIWYG BBCode and XHTML editor. Prior to version 3.2.1, attackers with the ability to control configuration options passed to sceditor.create() — such as emoticons, charset, and style — could trigger XSS attacks due to a lack of sanitization of these configuration options. This vulnerability has been addressed in version 3.2.1.

Critical Impact

Attackers can inject malicious scripts through unsanitized configuration options, potentially leading to session hijacking, data theft, or malicious actions performed on behalf of authenticated users.

Affected Products

• SCEditor versions prior to 3.2.1
• Applications implementing SCEditor with user-controllable configuration options
• Web platforms using SCEditor WYSIWYG functionality

Discovery Timeline

• 2026-02-06 - CVE CVE-2026-25581 published to NVD
• 2026-02-06 - Last updated in NVD database

Technical Details for CVE-2026-25581

Vulnerability Analysis

This vulnerability stems from insufficient input validation in SCEditor's initialization process. When developers integrate SCEditor into their applications, configuration options are passed to the sceditor.create() function. Prior to version 3.2.1, these configuration values were directly incorporated into the editor's HTML document without proper sanitization, creating an injection point for malicious scripts.

The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. An attacker who can influence the configuration parameters — particularly the style, charset, or color options — can inject arbitrary JavaScript that executes in the context of the victim's browser session.

The attack requires user interaction, as the victim must load a page containing the maliciously configured SCEditor instance. The scope is changed, meaning the vulnerability can impact resources beyond the vulnerable component's security scope, potentially affecting the parent application's DOM and user session.

Root Cause

The root cause is missing input sanitization for configuration options passed to sceditor.create(). The style option was written directly into the editor's HTML document without entity encoding, and the charset option lacked validation against a safe character set pattern. Additionally, color values in the default commands were not validated, allowing injection through the background-color CSS property.

Attack Vector

This vulnerability is exploitable via network-based attacks where an attacker can manipulate the configuration options passed to SCEditor. Attack scenarios include:

1. User-Generated Content Platforms: Applications allowing users to customize editor appearance could expose configuration options to manipulation
2. Configuration Injection: If configuration values are derived from URL parameters, cookies, or other user-controllable sources, attackers can inject malicious payloads
3. Supply Chain Attacks: Compromised configuration files or third-party integrations could introduce malicious configuration values

The following patch demonstrates the security fix implemented in version 3.2.1:

 		options.height || dom.height(original)
 	);
 
-		// Add ios to HTML so can apply CSS fix to only it
-		var className = browser.ios ? ' ios' : '';
+	if (!domPurify.isValidAttribute('link', 'href', options.style)) {
+		options.style = '';
+	}
+
+	if (!/^[a-z\-0-9 ]+$/i.test(options.charset)) {
+		options.charset = 'UTF-8';
+	}
 
 	wysiwygDocument = wysiwygEditor.contentDocument;
 	wysiwygDocument.open();
 	wysiwygDocument.write(_tmpl('html', {
-		attrs: ' class="' + className + '"',
+		// Add ios to HTML so can apply CSS fix to only it
+		attrs: browser.ios ? ' class="ios"' : '',
 		spellcheck: options.spellcheck ? '' : 'spellcheck="false"',
 		charset: options.charset,
-		style: options.style
-	}));
+		style: escape.entities(options.style)
+	}, false, false));
 	wysiwygDocument.close();
 
 	wysiwygBody = wysiwygDocument.body;

Source: GitHub Commit Changes

The patch introduces multiple security controls including DOMPurify validation for the style option, regex validation for charset to only allow alphanumeric characters with hyphens and spaces, and HTML entity encoding via escape.entities().

Additional sanitization was added for color options:

 				html += '<div class="sceditor-color-column">';
 
 				column.split(',').forEach(function (color) {
+					// Only allow named, #aaa, hsl(1.1 50% / 1), etc.
+					if (!/^[\#a-z0-9\-\(\) \/%\.]+$/i.test(color)) {
+						color = '';
+					}
+
 					html +=
 						'<a href="#" class="sceditor-color-option"' +
 						' style="background-color: ' + color + '"' +

Source: GitHub Commit Changes

Detection Methods for CVE-2026-25581

Indicators of Compromise

• Unusual JavaScript payloads in SCEditor configuration parameters
• Unexpected charset values containing special characters beyond alphanumeric and hyphens
• Malformed style URLs or inline styles containing JavaScript event handlers
• Browser console errors related to Content Security Policy violations from SCEditor iframes

Detection Strategies

• Implement Content Security Policy (CSP) headers to detect and block inline script execution
• Monitor web application logs for suspicious configuration parameters containing script tags or JavaScript event handlers
• Deploy Web Application Firewall (WAF) rules to detect XSS patterns in request parameters
• Use SentinelOne Singularity XDR to monitor for browser-based attacks and malicious script execution

Monitoring Recommendations

• Enable logging for all SCEditor configuration changes in production environments
• Set up alerts for CSP violation reports that originate from SCEditor components
• Monitor for unusual DOM modifications within SCEditor iframe elements
• Implement real-time behavioral analysis with SentinelOne to detect post-exploitation activities

How to Mitigate CVE-2026-25581

Immediate Actions Required

• Upgrade SCEditor to version 3.2.1 or later immediately
• Audit all instances where SCEditor configuration options are derived from user input
• Implement server-side validation for any configuration parameters before passing them to SCEditor
• Review application code for any user-controllable paths to SCEditor configuration

Patch Information

The vulnerability has been fixed in SCEditor version 3.2.1. The security patch (commit 5733aed4f0e257cb78e1ba191715fc458cbd473d) introduces proper sanitization for configuration options including DOMPurify validation for style attributes, regex-based charset validation, HTML entity encoding, and color value validation. For detailed patch information, see the GitHub Security Advisory.

Workarounds

• Ensure configuration options passed to sceditor.create() are hardcoded or sourced from trusted server-side configuration only
• Implement strict Content Security Policy headers to mitigate XSS impact (e.g., script-src 'self')
• Add input validation layer before SCEditor initialization to sanitize charset, style, and color options
• Use SentinelOne's runtime protection to detect and block malicious script execution attempts

# Example Content Security Policy header configuration (Apache)
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; frame-src 'self'"

# Example for Nginx
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; frame-src 'self'";