CVE-2022-24728: CKEditor4 XSS Vulnerability

CVE-2022-24728 Overview

CVE-2022-24728 is a Cross-Site Scripting (XSS) vulnerability discovered in CKEditor4, a widely-used open source WYSIWYG HTML editor. The vulnerability exists in the core HTML processing module and affects all plugins used by CKEditor 4 prior to version 4.18.0. An attacker can inject malformed HTML that bypasses content sanitization mechanisms, enabling the execution of arbitrary JavaScript code in the context of a victim's browser session.

This vulnerability is particularly significant due to CKEditor4's extensive deployment across content management systems, web applications, and enterprise platforms including Drupal, Oracle Application Express, and various Oracle Financial Services products.

Critical Impact

Successful exploitation allows attackers to execute arbitrary JavaScript code in user browsers, potentially leading to session hijacking, credential theft, defacement, or further malware distribution through affected web applications.

Affected Products

• CKEditor versions prior to 4.18.0
• Drupal Core (multiple versions)
• Oracle Application Express
• Oracle Commerce Merchandising 11.3.2
• Oracle Financial Services Analytical Applications Infrastructure (versions 8.0.7.0 through 8.1.2.1)
• Oracle Financial Services Behavior Detection Platform (versions 8.0.7.0 and 8.0.8.0)
• Oracle Financial Services Trade-Based Anti Money Laundering (8.0.7 and 8.0.8 Enterprise)
• Oracle PeopleSoft Enterprise PeopleTools (8.58 and 8.59)
• Fedora Project Fedora (36 and 37)

Discovery Timeline

• March 16, 2022 - CVE-2022-24728 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-24728

Vulnerability Analysis

The vulnerability resides in CKEditor4's core HTML processing module, which is responsible for parsing and sanitizing user-supplied HTML content before rendering it in the editor. Due to improper handling of malformed HTML input, the sanitization routines fail to adequately neutralize certain payloads, allowing crafted HTML to pass through unfiltered.

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The flaw affects all plugins that rely on the core HTML processing functionality, significantly expanding the attack surface across various CKEditor features.

The network-accessible nature of web-based editors means that authenticated users with low privileges can potentially inject malicious content. When other users interact with this content, their browsers execute the injected JavaScript, enabling attackers to perform actions on behalf of victims or steal sensitive session data.

Root Cause

The root cause of CVE-2022-24728 lies in insufficient input validation and sanitization within CKEditor4's HTML processing pipeline. The core module fails to properly handle edge cases involving malformed HTML structures, allowing specially crafted payloads to bypass the content sanitization filters. This incomplete sanitization enables script elements or event handlers embedded in malformed HTML to persist through the processing chain and execute when rendered in a user's browser.

Attack Vector

The attack is network-based and requires an authenticated user to submit malicious content through the CKEditor interface. The attacker crafts HTML that exploits parsing inconsistencies in the sanitization module, embedding JavaScript that survives the filtering process.

When a victim views or interacts with the compromised content, the malicious script executes within their browser context. This enables various attack scenarios including:

• Session token theft and account hijacking
• Keylogging and credential harvesting
• Phishing through DOM manipulation
• Propagation of malicious content to additional users

The attack requires user interaction—specifically, the victim must view or interact with content containing the malicious payload. The changed scope characteristic means the vulnerability can impact resources beyond the vulnerable component's security scope, potentially affecting the broader web application hosting CKEditor.

Detection Methods for CVE-2022-24728

Indicators of Compromise

• Unusual HTML content patterns in CKEditor submissions, particularly malformed HTML structures with embedded script tags or event handlers
• JavaScript execution errors or unexpected script activity when users interact with editor content
• Anomalous network requests originating from pages containing CKEditor components to unknown external domains
• User reports of unexpected browser behavior or authentication issues after interacting with editor content

Detection Strategies

• Monitor web application logs for submissions containing suspicious HTML patterns or script injection attempts to CKEditor endpoints
• Implement Content Security Policy (CSP) headers to detect and report inline script execution attempts
• Deploy web application firewalls (WAF) with rules targeting XSS payloads in form submissions
• Conduct regular vulnerability scanning to identify outdated CKEditor installations

Monitoring Recommendations

• Enable logging for all content submissions through CKEditor interfaces with sufficient detail to capture HTML payloads
• Configure browser-based CSP reporting to capture violation events indicating potential XSS exploitation
• Monitor for suspicious DOM modifications or unexpected script execution patterns in user sessions
• Track authentication events for signs of session hijacking following user interaction with editor content

How to Mitigate CVE-2022-24728

Immediate Actions Required

• Upgrade CKEditor4 to version 4.18.0 or later immediately across all affected deployments
• For Drupal installations, apply the security update referenced in Drupal Security Advisory SA-CORE-2022-005
• Oracle product users should apply the patches outlined in the Oracle Critical Patch Update July 2022
• Implement Content Security Policy headers to provide defense-in-depth against XSS attacks

Patch Information

CKEditor has released version 4.18.0 which addresses this vulnerability with improved HTML sanitization in the core processing module. The specific fix can be reviewed in commit d158413449692d920a778503502dcb22881bc949.

Organizations using CKEditor as a component in larger platforms should ensure updates are applied through the appropriate channels:

• Drupal: Apply updates as documented in SA-CORE-2022-005
• Oracle Products: Follow guidance in the Oracle Security Alert July 2022
• Fedora: Update packages via official Fedora repositories

For complete details on the 4.18.0 release, refer to the CKEditor 4.18.0 Release Notes.

Workarounds

• According to the security advisory, there are currently no known workarounds available for this vulnerability
• Organizations unable to immediately patch should implement strict Content Security Policy headers to limit script execution
• Consider temporarily disabling CKEditor functionality in high-risk environments until patching can be completed
• Implement additional input validation at the application layer as a supplementary control

# Example Content Security Policy header configuration (Apache)
# Add to .htaccess or virtual host configuration
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"