ProSolution WP Client Plugin Arbitrary File Upload Vulnerability (CVE-2026-2942)

The ProSolution WP Client plugin for WordPress, in versions up to and including 1.9.9, contains an arbitrary file upload vulnerability (CVE-2026-2942). The vulnerability stems from missing file type validation within the 'proSol_fileUploadProcess' function. This flaw allows unauthenticated attackers to upload arbitrary files to the affected server. Successful exploitation could lead to remote code execution (RCE), potentially giving the attacker complete control over the compromised WordPress instance. The vulnerability was reported by Wordfence and affects any WordPress site using the vulnerable plugin.

Attack Chain

1. An unauthenticated attacker identifies a WordPress site using a vulnerable version of the ProSolution WP Client plugin (<= 1.9.9).
2. The attacker crafts a malicious HTTP request targeting the 'proSol_fileUploadProcess' function.
3. The request includes a payload designed to upload an arbitrary file (e.g., a PHP script) to the server.
4. Due to the missing file type validation, the server accepts the uploaded file without proper sanitization or checks.
5. The attacker determines the upload path of the malicious file.
6. The attacker then crafts another HTTP request to execute the uploaded PHP script.
7. The PHP script executes arbitrary code on the server, potentially granting the attacker a web shell or other means of persistent access.
8. The attacker leverages the compromised server for malicious activities, such as data theft, defacement, or further lateral movement.

Impact

Successful exploitation of this vulnerability (CVE-2026-2942) allows unauthenticated attackers to upload arbitrary files to a vulnerable WordPress server. This can lead to remote code execution, potentially giving the attacker complete control over the compromised WordPress site. This could result in data breaches, website defacement, malware distribution, or the use of the compromised server for further attacks. Given the severity of RCE and the ease of exploitation, this vulnerability poses a significant risk to websites utilizing the affected plugin.

Recommendation

• Upgrade the ProSolution WP Client plugin to the latest version (greater than 1.9.9) to patch CVE-2026-2942.
• Implement a web application firewall (WAF) rule to block requests to 'proSol_fileUploadProcess' containing suspicious file extensions, mitigating the vulnerability even if patching is delayed.
• Monitor web server logs for unusual activity, such as requests to newly uploaded files in the WordPress uploads directory, to detect potential exploitation attempts. Use a Sigma rule to identify such activity in webserver logs.
• Enable and review WordPress audit logs for file modifications and plugin updates, providing insights into potential unauthorized changes.