CVE-2006-6278 in Alex Guestbook
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in index.php in @lex Guestbook 4.0.1 allows remote attackers to inject arbitrary web script or HTML via the skin parameter.
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Analysis
by VulDB Data Team • 09/28/2017
The CVE-2006-6278 vulnerability represents a classic cross-site scripting flaw in the @lex Guestbook 4.0.1 web application that fundamentally compromises user session integrity and data confidentiality. This vulnerability resides within the index.php file and specifically targets the skin parameter handling mechanism, creating an exploitable entry point for malicious actors to inject arbitrary web scripts or HTML content into the application's response. The flaw demonstrates a critical failure in input validation and output encoding practices that were prevalent in web applications of that era, particularly highlighting the insufficient sanitization of user-supplied parameters before their inclusion in dynamic web content.
The technical implementation of this vulnerability stems from the application's failure to properly escape or validate the skin parameter value before incorporating it into the HTML response sent to users. When a user submits a request containing a malicious skin parameter value, the application directly embeds this unvalidated input into the generated HTML without appropriate encoding or filtering mechanisms. This creates a persistent XSS vector where attackers can execute scripts in the context of other users' browsers, potentially leading to session hijacking, credential theft, or unauthorized actions performed on behalf of victims. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws resulting from inadequate input validation and output encoding practices. The attack surface is particularly concerning as it operates at the application layer, allowing threat actors to exploit the vulnerability through simple HTTP requests without requiring privileged access or complex exploitation techniques.
The operational impact of CVE-2006-6278 extends beyond immediate script execution capabilities to encompass broader security implications for web application integrity and user trust. When exploited successfully, this vulnerability enables attackers to manipulate guestbook entries, inject malicious content that persists across multiple user sessions, and potentially redirect users to phishing sites or malicious domains. The vulnerability affects the fundamental security model of the guestbook application by allowing unauthorized modification of content that should remain trusted and validated. Users who view affected guestbook entries become unwitting participants in the attack, executing malicious scripts in their browsers under the guise of legitimate application behavior. This type of vulnerability also aligns with ATT&CK technique T1566, which covers social engineering through malicious web content delivery, and demonstrates how legacy web applications often lack modern security controls such as Content Security Policy headers or comprehensive input validation frameworks that would prevent such attacks.
Mitigation strategies for CVE-2006-6278 require immediate implementation of proper input validation and output encoding mechanisms within the application code. The most effective remediation involves sanitizing all user-supplied parameters, particularly those used in dynamic content generation, through comprehensive validation that restricts input to expected formats and applies appropriate HTML encoding before inclusion in response content. Security practitioners should implement a whitelist approach for skin parameter values, accepting only predefined, safe options rather than allowing arbitrary input. Additionally, the application should be upgraded to a supported version that incorporates modern security practices including proper parameter validation, output encoding, and input sanitization. Organizations should also consider implementing Content Security Policy headers to provide additional defense-in-depth against XSS attacks, though this represents a secondary mitigation rather than a primary fix. The vulnerability serves as a historical example of why web application security must be integrated throughout the development lifecycle rather than addressed as an afterthought, emphasizing the critical need for secure coding practices and regular security assessments of web applications.