CVE-2020-12438 in php-fusion
Summary
by MITRE
An XSS vulnerability exists in the banners.php page of PHP-Fusion 9.03.50. This can be exploited because the only security measure used against XSS is the stripping of SCRIPT tags. A malicious actor can use HTML event handlers to run JavaScript instead of using SCRIPT tags.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability identified as CVE-2020-12438 represents a critical cross-site scripting weakness in PHP-Fusion version 9.03.50 specifically within the banners.php page functionality. This issue demonstrates a fundamental flaw in the application's security implementation where the developers relied solely on script tag removal as their primary defense mechanism against XSS attacks. The vulnerability stems from an insufficient security model that fails to account for the various methods attackers can employ to bypass simple tag filtering mechanisms.
The technical exploitation of this vulnerability occurs through the use of HTML event handlers which can execute JavaScript code without requiring the direct insertion of script tags. Common event handlers such as onclick, onload, onerror, and others provide alternative attack vectors that allow malicious actors to inject executable code into the application's output. These event handlers can be embedded within HTML elements like img, input, or div tags, creating a pathway for JavaScript execution that bypasses the basic script tag stripping mechanism. This approach aligns with CWE-79 which categorizes cross-site scripting vulnerabilities where untrusted data is improperly sanitized or escaped.
The operational impact of this vulnerability extends beyond simple data theft or session hijacking. Attackers can leverage this weakness to perform a range of malicious activities including but not limited to cookie theft, redirecting users to malicious domains, defacing the website content, or even executing more sophisticated attacks such as credential harvesting. The vulnerability affects the entire PHP-Fusion platform since banners.php is a core component used for displaying advertisements and promotional content. When exploited, this vulnerability can compromise user sessions, potentially allowing unauthorized access to administrative functions and persistent malicious code execution on the target system.
Security practitioners should implement multiple layers of defense to mitigate this vulnerability. The primary recommendation involves implementing comprehensive input validation and output encoding mechanisms that properly sanitize all user-supplied data before rendering it in the browser context. This approach should include the use of Content Security Policy headers, proper HTML encoding of all dynamic content, and the implementation of a whitelist-based approach for acceptable HTML elements and attributes. The mitigation strategy should also incorporate regular security audits and penetration testing to identify similar bypass techniques that may exist in other parts of the application. Organizations should follow ATT&CK framework tactics related to TA0001 (Initial Access) and TA0002 (Execution) by implementing proper input validation and output encoding controls to prevent exploitation of this type of vulnerability. Additionally, the implementation of a Web Application Firewall with advanced XSS detection capabilities can provide an additional protective layer against such attacks.