CVE-2016-10959 in estatik Plugin
Summary
by MITRE
The estatik plugin before 2.3.1 for WordPress has authenticated arbitrary file upload (exploitable with CSRF) via es_media_images[] to wp-admin/admin-ajax.php.
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Analysis
by VulDB Data Team • 12/25/2023
The estatik plugin for WordPress suffered from a critical authenticated arbitrary file upload vulnerability that could be exploited through a cross-site request forgery attack vector. This flaw affected versions prior to 2.3.1 and allowed authenticated attackers with minimal privileges to upload malicious files to the target WordPress installation. The vulnerability specifically existed in the wp-admin/admin-ajax.php endpoint which handled media image uploads through the es_media_images[] parameter. The issue stemmed from insufficient input validation and sanitization of file upload parameters, creating an exploitable path for privilege escalation and potential code execution.
The technical implementation of this vulnerability allowed attackers to bypass normal file upload restrictions by leveraging the plugin's media handling functionality. When the es_media_images[] parameter was submitted through the admin-ajax.php endpoint, the plugin failed to properly validate the file types and content, enabling the upload of arbitrary file formats including potentially malicious code. This authenticated arbitrary file upload vulnerability represents a direct violation of secure coding practices and falls under the CWE-434 category for Unrestricted Upload of File with Dangerous Type. The vulnerability's exploitation required only a valid WordPress user account with minimal privileges, making it particularly dangerous in environments where user access is not strictly controlled.
The operational impact of this vulnerability extended beyond simple file upload capabilities, as it could lead to complete system compromise through various attack vectors. An attacker could upload web shells, malicious PHP scripts, or other exploit payloads that would execute with the privileges of the affected WordPress installation. This vulnerability could facilitate further attacks including lateral movement within network environments, data exfiltration, and establishment of persistent access points. The combination of authenticated access with CSRF exploitation meant that attackers could potentially leverage this vulnerability through social engineering or compromised user sessions, significantly expanding the attack surface and reducing the required attack complexity.
Mitigation strategies for this vulnerability required immediate patching to version 2.3.1 or later, which addressed the input validation flaws in the file upload handling code. Organizations should also implement additional security measures including restricting file upload capabilities, implementing proper file type validation, and monitoring for suspicious file upload activities. Network segmentation and privilege separation could help limit the potential impact of successful exploitation. The vulnerability aligns with ATT&CK technique T1078 for Valid Accounts and T1059 for Command and Scripting Interpreter, as it allows for both credential-based access and execution of malicious code. Regular security audits and vulnerability assessments should include checks for similar unvalidated file upload patterns in WordPress plugins and themes to prevent similar issues from occurring in other components of the web application ecosystem.