CVE-2013-5963 in Simple Dropbox Upload Form
Summary
by MITRE
Unrestricted file upload vulnerability in multi.php in Simple Dropbox Upload plugin before 1.8.8.1 for WordPress allows remote attackers to execute arbitrary code by uploading a file with an executable extension, then accessing it via a direct request to the file in wp-content/uploads/wpdb/.
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Analysis
by VulDB Data Team • 01/08/2022
The vulnerability identified as CVE-2013-5963 represents a critical unrestricted file upload flaw within the Simple Dropbox Upload plugin for WordPress systems. This issue affects versions prior to 1.8.8.1 and creates a significant security risk by allowing remote attackers to bypass file validation mechanisms and upload malicious files to the target system. The vulnerability specifically resides in the multi.php script component of the plugin, which fails to properly validate file extensions and content types during the upload process. Attackers can exploit this weakness by uploading files with executable extensions such as .php, .asp, or .jsp, which can then be executed on the web server, potentially leading to complete system compromise.
The technical exploitation of this vulnerability follows a straightforward but dangerous methodology where malicious actors first upload a payload file through the vulnerable plugin interface. The upload process does not adequately verify file extensions or examine file content, allowing attackers to bypass security checks that should prevent execution of potentially harmful code. Once uploaded, these files become accessible through direct requests to the wp-content/uploads/wpdb/ directory, where they can be executed by the web server. This creates a persistent backdoor that attackers can use to maintain access, escalate privileges, or deploy additional malware. The vulnerability directly maps to CWE-434, which defines unrestricted upload of executable code as a well-known security weakness that enables arbitrary code execution.
From an operational standpoint, this vulnerability presents severe implications for WordPress installations using the affected plugin version. Organizations running vulnerable systems face immediate risks including data breaches, system takeover, and potential lateral movement within their network infrastructure. The attack surface expands significantly as attackers can leverage this vulnerability to establish persistent access, deploy web shells, or use the compromised system as a launching point for further attacks. The impact extends beyond individual site compromise, as WordPress installations often serve as entry points for broader enterprise attacks, particularly when multiple sites share common infrastructure or when administrators reuse compromised credentials across systems. This vulnerability also aligns with ATT&CK technique T1190, which describes the use of vulnerable applications to gain initial access and establish a foothold in target environments.
Mitigation strategies for CVE-2013-5963 require immediate action to address the root cause through plugin updates to version 1.8.8.1 or later, which includes proper file validation mechanisms. Organizations should implement additional security layers including restrictive file upload policies, content type validation, and proper file extension filtering at multiple points in the upload pipeline. Server-side configurations should enforce strict permissions on upload directories and disable execution of uploaded files through web server configurations. Network-level protections such as web application firewalls can provide additional detection and prevention capabilities, while regular security audits should verify that no malicious files remain in the upload directories. System administrators should also consider implementing automated monitoring solutions to detect unusual file upload patterns or unauthorized access attempts to upload directories, as these activities often precede successful exploitation attempts.