CVE-2015-9539 in Fast Secure Contact Form Plugin
Summary
by MITRE
The Fast Secure Contact Form plugin before 4.0.38 for WordPress allows fs_contact_form1[welcome] XSS.
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Analysis
by VulDB Data Team • 02/28/2024
The Fast Secure Contact Form plugin for WordPress suffered from a cross-site scripting vulnerability in versions prior to 4.0.38 that affected the fs_contact_form1[welcome] parameter. This vulnerability classified under CWE-79, which represents Cross-Site Scripting, represents a critical security flaw that could allow attackers to inject malicious scripts into web pages viewed by other users. The vulnerability specifically targeted the welcome message functionality within the contact form plugin, making it a prime target for exploitation in web application attacks.
The technical implementation of this vulnerability stemmed from insufficient input validation and output encoding within the plugin's processing of the welcome parameter. When administrators configured welcome messages for contact form submissions, the plugin failed to properly sanitize user-supplied input before rendering it in the web page context. This lack of proper sanitization allowed malicious actors to inject script code that would execute in the browsers of unsuspecting users who visited pages containing the vulnerable form elements. The vulnerability existed in the plugin's handling of user data without appropriate context-aware encoding mechanisms that would neutralize potentially dangerous characters and sequences.
The operational impact of this vulnerability extended beyond simple script injection, creating significant risks for WordPress sites utilizing the affected plugin version. Attackers could exploit this weakness to steal session cookies, redirect users to malicious websites, or perform actions on behalf of authenticated users. The vulnerability particularly threatened administrators and site owners who might unknowingly include malicious code in welcome messages, as the XSS attack could be triggered when legitimate users interacted with the contact form. This made the vulnerability particularly dangerous in environments where the plugin was widely used and where administrators might not fully understand the security implications of their configuration choices.
Mitigation strategies for this vulnerability required immediate action including upgrading to version 4.0.38 or later where the plugin properly implemented input sanitization and output encoding for the welcome parameter. Security practitioners should also implement additional protective measures such as content security policies that restrict script execution and monitor for suspicious activity in contact form submissions. The vulnerability highlighted the importance of proper input validation and output encoding practices in web applications, aligning with ATT&CK technique T1203 for Exploitation for Credential Access and T1566 for Phishing. Organizations should conduct regular security assessments of their WordPress plugins and maintain updated security practices to prevent similar vulnerabilities from compromising their web applications. The incident reinforced the critical need for secure coding practices that prevent XSS vulnerabilities through proper data validation and encoding mechanisms.