CVE-2015-1494 in Fancybox
Summary
by MITRE
The FancyBox for WordPress plugin before 3.0.3 for WordPress does not properly restrict access, which allows remote attackers to conduct cross-site scripting (XSS) attacks via an mfbfw[*] parameter in an update action to wp-admin/admin-post.php, as demonstrated by the mfbfw[padding] parameter and exploited in the wild in February 2015.
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Analysis
by VulDB Data Team • 11/30/2024
The FancyBox for WordPress plugin vulnerability represents a critical access control flaw that enabled remote attackers to execute cross-site scripting attacks through improper input validation and sanitization. This vulnerability affected versions prior to 3.0.3 and specifically targeted the wp-admin/admin-post.php endpoint, which serves as a central administrative processing point for WordPress plugins. The flaw exploited the plugin's failure to properly validate and sanitize user-supplied parameters, creating an avenue for malicious actors to inject arbitrary JavaScript code into the administrative interface. The attack vector was particularly insidious because it leveraged legitimate administrative functions while bypassing standard security mechanisms that should have prevented unauthorized parameter manipulation.
The technical exploitation occurred through the mfbfw[*] parameter family, with the mfbfw[padding] parameter serving as a primary attack vector in February 2015. This parameter was processed within the plugin's update functionality without adequate input filtering, allowing attackers to inject malicious JavaScript payloads that would execute in the context of administrators' browsers. The vulnerability aligns with CWE-79, which describes cross-site scripting flaws where untrusted data is incorporated into web pages without proper validation or sanitization. The flaw represents a classic case of insufficient input validation and improper output encoding, where the plugin failed to implement proper parameter sanitization before processing administrative requests.
The operational impact of this vulnerability was severe as it provided attackers with a persistent means of compromising WordPress installations through the administrative interface. Once an administrator visited a malicious page or interacted with compromised content, the injected JavaScript could execute with full administrative privileges, potentially leading to complete system compromise. This vulnerability enabled attackers to perform actions such as modifying plugin settings, creating new administrator accounts, stealing session cookies, or redirecting users to malicious sites. The attack's effectiveness was amplified by the fact that it required no prior authentication and could be exploited through social engineering techniques or by targeting vulnerable sites that had not yet applied the patch.
Mitigation strategies for this vulnerability centered on immediate patch application to version 3.0.3 or later, which implemented proper parameter validation and sanitization. Organizations should have conducted comprehensive vulnerability assessments to identify affected installations and implemented network monitoring to detect exploitation attempts. The remediation process required careful attention to plugin compatibility and backup restoration procedures to ensure smooth updates. Additionally, implementing web application firewalls and input validation rules at the network level provided additional defense-in-depth measures. This vulnerability underscores the importance of proper access control mechanisms and input validation in plugin development, aligning with ATT&CK technique T1059.007 for script injection and T1071.001 for application layer protocols. The incident highlighted the critical need for regular security updates and proper code review processes in WordPress plugin development to prevent similar vulnerabilities from being introduced into production environments.