CVE-2020-9440 in WSC Plugin
Summary
by MITRE
A cross-site scripting (XSS) vulnerability in the WSC plugin through 5.5.7.5 for CKEditor 4 allows remote attackers to run arbitrary web script inside an IFRAME element by injecting a crafted HTML element into the editor.
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Analysis
by VulDB Data Team • 04/11/2024
The CVE-2020-9440 vulnerability represents a critical cross-site scripting flaw within the WSC plugin version 5.5.7.5 for CKEditor 4, exposing web applications to sophisticated attack vectors that can compromise user sessions and data integrity. This vulnerability specifically targets the plugin's handling of HTML content within the CKEditor interface, creating a pathway for malicious actors to inject persistent script code that executes within the context of legitimate user sessions. The WSC plugin, designed to provide spell checking capabilities, becomes a vector for exploitation when it fails to properly sanitize user input before rendering content within IFRAME elements, which are commonly used for embedding third-party content and maintaining isolation between different application components.
The technical exploitation of this vulnerability occurs through careful crafting of HTML elements that bypass the editor's input validation mechanisms, allowing attackers to inject malicious scripts that execute within the IFRAME context where the CKEditor is rendered. This flaw stems from inadequate sanitization of user-provided content, specifically when the WSC plugin processes text that contains HTML markup without proper context-aware filtering. The vulnerability manifests when the plugin's HTML processing logic fails to distinguish between legitimate content and potentially harmful script tags, enabling attackers to inject JavaScript code that can access cookies, session tokens, or other sensitive information. According to CWE classification, this represents a CWE-79: Cross-site Scripting vulnerability, specifically categorized under the "Improper Neutralization of Input During Web Page Generation" subtype, which aligns with the plugin's failure to properly validate and sanitize HTML content before rendering.
The operational impact of CVE-2020-9440 extends beyond simple script execution, as it can enable attackers to perform session hijacking, deface web applications, or redirect users to malicious sites. When users interact with compromised CKEditor instances, the injected scripts can harvest authentication tokens, monitor user keystrokes, or manipulate the application's functionality to serve malicious purposes. The vulnerability is particularly dangerous in environments where CKEditor is used for content management, user-generated content systems, or collaborative platforms where multiple users interact with the same editing interface. Attackers can leverage this vulnerability through various attack vectors including phishing campaigns, social engineering, or by compromising content management systems that utilize the vulnerable plugin, potentially leading to full system compromise or data exfiltration. The ATT&CK framework categorizes this vulnerability under T1059.001 - Command and Scripting Interpreter: JavaScript, as it enables attackers to execute JavaScript code within the victim's browser context, and T1531 - Account Access Removal, when attackers use the compromised session to escalate privileges or access sensitive resources.
Mitigation strategies for CVE-2020-9440 require immediate patching of the WSC plugin to version 5.5.7.6 or later, which includes proper HTML sanitization and input validation mechanisms. Organizations should implement comprehensive content security policies that restrict script execution within IFRAME elements and enforce strict input validation at multiple layers of the application stack. The implementation of Content Security Policy headers can provide additional protection by preventing unauthorized script execution even if the vulnerability is exploited. Regular security audits of web applications should include checks for vulnerable CKEditor plugin versions, and organizations should consider implementing automated vulnerability scanning tools that can detect the presence of known vulnerable components. Additionally, user education regarding the risks of interacting with untrusted content and implementing proper access controls within CKEditor configurations can help reduce the attack surface and limit the potential impact of successful exploitation attempts.