CVE-2006-6978 in FCKEditor
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the "Basic Toolbar Selection" in FCKEditor allows remote attackers to execute arbitrary JavaScript via the javascript: URI in the (1) href or (2) onmouseover attribute of the A HTML tag.
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Analysis
by VulDB Data Team • 10/13/2017
The vulnerability described in CVE-2006-6978 represents a critical cross-site scripting flaw within the FCKEditor content management system that has significant implications for web application security. This vulnerability specifically targets the "Basic Toolbar Selection" feature of FCKEditor, which serves as a rich text editing interface commonly integrated into web applications for content creation and management. The flaw enables remote attackers to inject malicious JavaScript code through carefully crafted input that gets processed by the editor's toolbar functionality, creating a persistent vector for exploitation across multiple web applications that utilize this editor component.
The technical mechanism of this vulnerability stems from inadequate input validation and sanitization within the FCKEditor's processing of HTML attributes, particularly the href and onmouseover attributes of anchor tags. When users interact with the editor's toolbar and input malicious javascript: URIs, the system fails to properly filter or escape these dangerous input patterns before rendering them in the final HTML output. This processing failure occurs at the point where the editor handles user-provided content through its basic toolbar interface, which is designed to allow users to create and modify hyperlinks. The vulnerability specifically leverages the fact that the editor does not adequately sanitize the javascript: protocol within URI schemes, allowing attackers to inject executable JavaScript code that gets executed in the context of other users' browsers when they view the affected content.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious websites. When exploited, the vulnerability allows attackers to inject JavaScript code that can access user sessions, steal cookies, modify page content, or redirect users to phishing sites. The attack vector is particularly dangerous because it can be triggered through normal user interactions with the editor's toolbar, making it difficult to detect and prevent. This vulnerability affects any web application that uses FCKEditor and fails to implement additional security measures, potentially compromising thousands of users who interact with content created through the vulnerable editor.
Security professionals should understand that this vulnerability maps directly to CWE-79, which specifically addresses Cross-Site Scripting flaws in software applications. The ATT&CK framework categorizes this as a technique for code injection and privilege escalation, as attackers can leverage the vulnerability to execute arbitrary code in the context of other users. The vulnerability's classification as a remote code execution vector through browser-based attacks places it within the critical severity category, as it requires no local access and can be exploited through web-based interfaces. Organizations should implement comprehensive input validation, output encoding, and security headers to mitigate this risk, while also ensuring that all instances of FCKEditor are updated to versions that address this specific vulnerability. The remediation process must include thorough code review of all content management interfaces that utilize this editor component and implementation of proper HTML sanitization techniques to prevent similar vulnerabilities in other components.
The broader implications of this vulnerability highlight the importance of secure coding practices and the need for comprehensive security testing of web applications. This flaw demonstrates how seemingly innocuous features like rich text editors can become attack vectors when proper input validation is not implemented, emphasizing the critical need for defense-in-depth strategies that include both server-side and client-side security measures. The vulnerability also underscores the importance of keeping third-party components updated and monitoring for security advisories, as outdated libraries often contain known vulnerabilities that attackers can exploit to compromise entire web applications.