CVE-2013-1916 in User Photo Plugin
Summary
by MITRE • 06/24/2022
In WordPress Plugin User Photo 0.9.4, when a photo is uploaded, it is only partially validated and it is possible to upload a backdoor on the server hosting WordPress. This backdoor can be called (executed) even if the photo has not been yet approved.
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Analysis
by VulDB Data Team • 04/02/2025
The vulnerability identified as CVE-2013-1916 represents a critical security flaw in the WordPress Plugin User Photo version 0.9.4 that exposes systems to remote code execution risks. This issue stems from inadequate input validation mechanisms within the plugin's file upload functionality, creating a pathway for malicious actors to compromise WordPress installations. The vulnerability specifically affects the photo upload processing logic where file validation occurs only at a superficial level, allowing attackers to bypass security measures and deploy malicious payloads alongside legitimate user content. The flaw exists in the plugin's handling of user-uploaded files, where the system fails to perform comprehensive validation checks before accepting and storing uploaded media. This partial validation creates a window of opportunity for attackers to exploit the system by uploading files containing malicious code, effectively establishing a backdoor that can be executed at any time regardless of the photo's approval status. The security implications extend beyond simple file upload capabilities as the vulnerability allows for persistent access to the compromised system.
The technical exploitation of this vulnerability follows a well-defined attack pattern that aligns with common web application security flaws categorized under CWE-434, which addresses "Unrestricted Upload of File with Dangerous Type." The plugin's failure to implement proper file type checking, content validation, and sanitization creates a direct pathway for attackers to upload executable files or scripts that can be executed within the web server context. This vulnerability enables attackers to bypass standard WordPress security controls and gain unauthorized access to the underlying server infrastructure. The execution of malicious code occurs through the web server's interpretation of uploaded files, allowing attackers to establish persistent backdoors, execute arbitrary commands, and potentially escalate privileges within the compromised environment. The vulnerability's impact is amplified by the fact that the backdoor remains functional even when the photo upload is not approved, meaning that attackers can maintain access without requiring additional approval processes or user interaction. This characteristic makes the vulnerability particularly dangerous as it provides continuous access to compromised systems.
The operational impact of CVE-2013-1916 extends far beyond the immediate compromise of individual WordPress installations, creating widespread security risks across multiple organizations and systems. Attackers can leverage this vulnerability to establish persistent access points within networks, potentially using the compromised WordPress installations as launching pads for further attacks against internal systems. The vulnerability affects the fundamental security model of WordPress plugins, demonstrating how third-party extensions can introduce critical flaws that undermine the overall security posture of web applications. Organizations using affected versions of the User Photo plugin face significant risks including data theft, system compromise, and potential regulatory compliance violations. The vulnerability's persistence mechanism means that once exploited, the backdoor remains active even after the initial compromise, allowing attackers to maintain long-term access to compromised systems. This characteristic also complicates forensic analysis and incident response efforts as the malicious code can remain undetected for extended periods.
Mitigation strategies for CVE-2013-1916 require immediate action to address the specific vulnerability while implementing broader security practices to prevent similar issues. Organizations should immediately disable or remove the affected User Photo plugin version 0.9.4 from all WordPress installations and upgrade to a patched version if available. The recommended approach involves implementing comprehensive file validation mechanisms that check file extensions, MIME types, and content signatures before accepting uploads. Security measures should include restricting file upload capabilities to specific, safe file types and implementing proper file name sanitization to prevent directory traversal attacks. System administrators should also deploy web application firewalls and intrusion detection systems to monitor for suspicious upload activities and malicious file execution patterns. The vulnerability highlights the importance of proper input validation and output encoding practices as outlined in the OWASP Top Ten security framework, specifically addressing the risks associated with insecure file handling and improper validation of user-supplied data. Additionally, organizations should conduct regular security assessments of all installed plugins and themes to identify and remediate similar vulnerabilities across their WordPress ecosystems.