How to remediate – Uploader Plugin for WordPress File Upload Arbitrary Code Execu…

1. Introduction

The Uploader Plugin for WordPress contains a file upload vulnerability which allows arbitrary code execution on affected servers. This means an attacker could gain control of your website and potentially its underlying server. Websites using the Uploader Plugin are at risk, particularly those with public-facing uploads. Successful exploitation impacts confidentiality, integrity, and availability of data.

2. Technical Explanation

The vulnerability occurs because the plugin does not sufficiently check files uploaded by users. An attacker can upload a malicious PHP file which is then executed by the web server. This allows them to run commands on the system with the permissions of the web server user. No authentication is required for this attack, making it easier to exploit.

• Exploit mechanism: An attacker uploads a PHP file containing malicious code via the plugin’s upload functionality. The server then executes this file as if it were legitimate website code. For example, uploading a file with `` allows command execution through a URL parameter.
• Scope: WordPress websites using the Uploader Plugin are affected. Specific versions have not been identified in the provided information.

3. Detection and Assessment

Confirming vulnerability requires checking for the presence of the plugin and assessing its configuration. A thorough scan is recommended.

• Quick checks: Check your WordPress plugins list within the admin interface to confirm if the Uploader Plugin is installed.
• Scanning: Nessus ID d052c6cc can detect this vulnerability, but results should be verified.
• Logs and evidence: Examine web server access logs for unusual file uploads or execution of PHP files in the plugin’s upload directory. Look for requests containing suspicious characters or extensions.

wp plugin list | grep uploader

4. Solution / Remediation Steps

Currently, a specific solution is unknown. The following steps outline general best practices while awaiting an official patch.

4.1 Preparation

• Ensure you have access to restore from backup in case of issues. A rollback plan involves restoring the previous backup.
• A change window may be required depending on your environment and risk tolerance. Approval should be sought from relevant IT stakeholders.

4.2 Implementation

1. Step 1: Disable the Uploader Plugin within the WordPress admin interface. This will prevent further uploads, but does not remove existing malicious files.
2. Step 2: Scan your website’s file system for any uploaded files associated with the plugin. Pay close attention to directories used for storing uploads.
3. Step 3: Delete any suspicious or unknown files found in the upload directory. Be careful not to delete legitimate website content.

4.3 Config or Code Example

Before

// No specific code example available, as the vulnerability is in file handling logic. Plugin enabled with default settings.

After

// Plugin disabled within WordPress admin interface. No further uploads possible.

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help mitigate this type of vulnerability.

• Practice 1: Least privilege – Run the web server user with minimal necessary permissions to limit damage from exploitation.
• Practice 2: Input validation – Implement strict checks on all user-supplied data, including file uploads, to block malicious content.

4.5 Automation (Optional)

No automation is provided due to the lack of a specific fix and potential for disruption.

5. Verification / Validation

Confirming the fix involves verifying the plugin is disabled and re-testing upload functionality.

• Post-fix check: Check that the Uploader Plugin is listed as inactive within the WordPress admin interface.
• Re-test: Attempt to upload a test PHP file through the plugin’s upload form. The upload should fail or be blocked.
• Monitoring: Monitor web server logs for any attempts to access files in the plugin’s upload directory.

wp plugin list | grep uploader

6. Preventive Measures and Monitoring

Proactive measures can reduce the risk of similar vulnerabilities.

• Baselines: Update your WordPress security baseline to include regular plugin updates and vulnerability scanning.
• Asset and patch process: Establish a regular schedule for reviewing and applying security patches to all WordPress components, including plugins.

7. Risks, Side Effects, and Roll Back

Disabling the plugin may impact website functionality that relies on file uploads.

• Risk or side effect 2: Removing files from the upload directory may inadvertently delete legitimate content if not carefully reviewed.
• Roll back: Re-enable the Uploader Plugin within the WordPress admin interface to restore previous functionality. Restore any deleted files from backup if necessary.

8. References and Resources

Links related to this specific vulnerability.

• Vendor advisory or bulletin: No official advisory is available at this time.
• NVD or CVE entry: No CVE entry is currently associated with this vulnerability.
• Product or platform documentation relevant to the fix: http://www.nessus.org/u?d052c6cc