CVE-2026-2942: ProSolution WP Client RCE Vulnerability

CVE-2026-2942 Overview

The ProSolution WP Client plugin for WordPress contains a critical arbitrary file upload vulnerability due to missing file type validation in the proSol_fileUploadProcess function. This vulnerability affects all versions up to and including 1.9.9, allowing unauthenticated attackers to upload arbitrary files to the affected site's server, which may result in remote code execution.

Critical Impact

Unauthenticated attackers can upload malicious files (such as PHP webshells) to WordPress servers, potentially achieving complete site takeover and remote code execution without any authentication.

Affected Products

• ProSolution WP Client plugin for WordPress versions up to and including 1.9.9
• WordPress sites running vulnerable versions of the ProSolution WP Client plugin

Discovery Timeline

• April 8, 2026 - CVE-2026-2942 published to NVD
• April 8, 2026 - Last updated in NVD database

Technical Details for CVE-2026-2942

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type). The proSol_fileUploadProcess function in the ProSolution WP Client plugin lacks proper file type validation, creating a critical security gap that allows attackers to bypass intended restrictions and upload files with any extension to the server.

The vulnerability is particularly severe because it requires no authentication to exploit. An unauthenticated remote attacker can craft a malicious request to the file upload endpoint and submit arbitrary file content, including executable PHP scripts. Once uploaded, these files can be accessed directly through the web server, enabling the attacker to execute arbitrary code in the context of the web application.

Root Cause

The root cause of this vulnerability lies in the absence of file type validation within the proSol_fileUploadProcess function located in class-prosolwpclient-public.php. The function processes file uploads without verifying that the uploaded file matches an allowed MIME type or file extension whitelist. This design flaw allows any file type to be accepted and stored on the server, including executable scripts.

Attack Vector

The attack vector is network-based and can be exploited remotely by unauthenticated attackers. The exploitation process involves:

1. Identifying a WordPress site running a vulnerable version of the ProSolution WP Client plugin
2. Crafting a malicious HTTP POST request to the file upload endpoint
3. Uploading a PHP webshell or other malicious script disguised as a legitimate file
4. Accessing the uploaded file directly via the web server to execute arbitrary commands

The vulnerability is accessible without any user interaction, authentication, or special privileges, making it highly exploitable by opportunistic attackers scanning for vulnerable WordPress installations.

For technical details on the vulnerable code, see the WordPress Plugin Source Code.

Detection Methods for CVE-2026-2942

Indicators of Compromise

• Unexpected PHP files or other executable scripts appearing in WordPress upload directories
• Web server logs showing POST requests to ProSolution WP Client file upload endpoints from unknown sources
• Suspicious outbound network connections from the web server
• New or modified files in the wp-content/uploads directory with unusual names or extensions
• Evidence of webshell activity such as command execution patterns in access logs

Detection Strategies

• Monitor file system changes in WordPress upload directories for newly created executable files
• Implement web application firewall (WAF) rules to inspect file upload requests for malicious content
• Review web server access logs for suspicious POST requests to plugin endpoints
• Use file integrity monitoring to detect unauthorized modifications to web-accessible directories
• Deploy endpoint detection solutions to identify webshell behavior and post-exploitation activity

Monitoring Recommendations

• Enable detailed logging for file upload operations in WordPress
• Configure alerts for new executable file creation in web-accessible directories
• Implement network monitoring to detect command-and-control communications from compromised servers
• Regularly audit installed WordPress plugins for known vulnerabilities

How to Mitigate CVE-2026-2942

Immediate Actions Required

• Update the ProSolution WP Client plugin to the latest patched version immediately
• Audit WordPress upload directories for any suspicious or unexpected files
• Review web server logs for evidence of exploitation attempts
• Consider temporarily disabling the plugin if an update is not immediately available
• Implement WAF rules to block malicious file upload attempts

Patch Information

A security patch has been released to address this vulnerability. The fix can be reviewed in the WordPress Plugin Changeset. Site administrators should update to the latest version of the ProSolution WP Client plugin that includes proper file type validation in the proSol_fileUploadProcess function.

For additional vulnerability details, see the Wordfence Vulnerability Report.

Workarounds

• Temporarily disable the ProSolution WP Client plugin until a patch can be applied
• Implement server-side restrictions to prevent execution of uploaded files in the uploads directory
• Configure a web application firewall to block requests containing executable file extensions
• Add .htaccess rules to prevent PHP execution in upload directories

# Add to .htaccess in wp-content/uploads directory to prevent PHP execution
<Files *.php>
    deny from all
</Files>

# Alternative: Disable script execution entirely in uploads
<Directory /path/to/wordpress/wp-content/uploads>
    php_admin_flag engine off
</Directory>