CVE-2023-6889 in phpmyfaq
Summary
by MITRE • 12/16/2023
Cross-site Scripting (XSS) - Stored in GitHub repository thorsten/phpmyfaq prior to 3.1.17.
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Analysis
by VulDB Data Team • 07/01/2026
Cross-site scripting vulnerabilities represent one of the most prevalent and dangerous web application security flaws, enabling attackers to inject malicious scripts into web pages viewed by other users. The stored cross-site scripting vulnerability identified in the thorsten/phpmyfaq GitHub repository prior to version 3.1.17 demonstrates how insufficient input validation and output encoding can create persistent attack vectors that compromise user sessions and data integrity. This particular flaw allows authenticated attackers with privileges to add content to the application to inject malicious JavaScript code that persists in the database and executes whenever other users view the affected content, making it a particularly insidious form of XSS attack.
The technical implementation of this stored XSS vulnerability stems from inadequate sanitization of user input within the phpmyfaq application's content management system. When administrators or authorized users submit content through the web interface, the application fails to properly validate or escape special characters in the submitted data before storing it in the database. This allows malicious payloads containing script tags or other executable code to be stored persistently and executed whenever the content is rendered to other users. The vulnerability operates at the application layer where user-supplied data flows through multiple processing stages including database storage and HTML rendering without proper security controls. According to CWE-79, this represents a classic case of insufficient input validation where the application does not adequately sanitize user-provided data before incorporating it into dynamically generated HTML content.
The operational impact of this stored XSS vulnerability extends beyond simple script execution to potentially compromise entire user sessions and enable advanced attack techniques. An attacker could inject malicious scripts that steal session cookies, redirect users to phishing sites, or even execute commands on behalf of authenticated users with elevated privileges. The persistence of the vulnerability means that once exploited, the malicious code continues to affect all users who access the affected content until the application is updated to address the flaw. This makes stored XSS particularly dangerous compared to reflected XSS variants, as the attack payload remains active and can affect multiple victims over extended periods without requiring additional user interaction. The vulnerability also aligns with ATT&CK technique T1566.001 which describes credential access through phishing campaigns that may leverage XSS vulnerabilities to establish initial compromise.
Mitigation strategies for this stored XSS vulnerability require comprehensive input validation and output encoding mechanisms throughout the application's data flow. Organizations should implement proper HTML escaping routines before displaying any user-generated content, ensuring that special characters are properly encoded to prevent script execution. The phpmyfaq developers addressed this issue by implementing stricter input sanitization and output encoding in version 3.1.17, which includes enhanced validation of submitted content and proper escaping of user data during rendering processes. Additionally, organizations should deploy web application firewalls that can detect and block known XSS attack patterns, implement content security policies to restrict script execution, and conduct regular security testing including automated scanning and manual penetration testing to identify similar vulnerabilities in other components. The vulnerability also underscores the importance of following secure coding practices such as those outlined in OWASP Top Ten and ISO/IEC 27001 standards for web application security.