CVE-2009-3539 in Ultra Classifieds Pro
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in YourFreeWorld Ultra Classifieds Pro allow remote attackers to inject arbitrary web script or HTML via the (1) cname parameter to subclass.php and the (2) sn parameter to listads.php.
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Analysis
by VulDB Data Team • 09/21/2025
The vulnerability described in CVE-2009-3539 represents a critical cross-site scripting flaw affecting the YourFreeWorld Ultra Classifieds Pro application. This vulnerability exists within the web application's input validation mechanisms, specifically targeting two distinct parameters that process user-supplied data without proper sanitization. The flaw allows remote attackers to execute malicious scripts in the context of other users' browsers, potentially leading to session hijacking, credential theft, or unauthorized actions within the application's security boundaries.
The technical implementation of this vulnerability stems from insufficient validation and sanitization of user input parameters. Attackers can exploit the cname parameter in subclass.php and the sn parameter in listads.php to inject malicious code that will be executed when other users view the affected pages. These parameters likely receive data from URL query strings or form submissions and are processed directly into HTML output without appropriate encoding or filtering. The vulnerability manifests as a classic reflected XSS attack where malicious payloads are reflected back to users through the vulnerable application's response, making it particularly dangerous as it requires no persistent storage of malicious content.
The operational impact of this vulnerability extends beyond simple script execution, as it creates a potential attack vector for more sophisticated exploitation techniques. An attacker could craft malicious URLs containing XSS payloads that, when clicked by unsuspecting users, would execute scripts in their browser context. This could lead to session fixation attacks, where attackers steal user authentication tokens, or more severe attacks involving data exfiltration from the victim's browser. The vulnerability affects the application's core functionality by potentially compromising the integrity of user interactions and the confidentiality of sensitive information processed through the classifieds system.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms. The application must sanitize all user-supplied input parameters, particularly those used in URL query strings, through proper encoding techniques such as HTML entity encoding before rendering any user data in the application's output. Additionally, implementing a Content Security Policy (CSP) would provide an additional layer of protection by restricting the sources from which scripts can be loaded and executed. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and represents a clear violation of secure coding practices that should be addressed through proper input validation as outlined in the OWASP Top Ten security risks. Organizations should also implement regular security assessments and code reviews to identify and remediate similar vulnerabilities in their web applications.
The exploitation of this vulnerability demonstrates the importance of maintaining secure coding practices throughout the software development lifecycle, particularly in applications handling user-generated content. The flaw represents a fundamental security weakness that could be exploited by attackers with minimal technical expertise, making it a significant concern for any organization relying on classifieds or similar web applications. Regular patching and security updates are essential to address such vulnerabilities, as they represent persistent threats that can be leveraged for extended periods if left unaddressed. This vulnerability also highlights the need for comprehensive security training for developers to prevent similar issues in future application development projects, ensuring that proper input validation and output encoding are implemented as standard development practices.