What the vulnerability does
01Description
The Drag and Drop Multiple File Upload for Contact Form 7 plugin for WordPress is vulnerable to arbitrary file upload in versions up to, and including, 1.3.9.7. This is due to insufficient file type validation that occurs when custom blacklist types are configured, which replaces the default dangerous extension denylist instead of merging with it, and the wpcf7_antiscript_file_name() sanitization function being bypassed for filenames containing non-ASCII characters. This makes it possible for unauthenticated attackers to upload arbitrary files, such as PHP files, to the server, which can be leveraged to achieve remote code execution. The vulnerability was originally reported by Leonid Semenenko (lsemenenko) and partially patched in version 1.3.9.7. A bypass for the patch was separately discovered and reported by Nguyen Hung (Mitchell).
Explanation of Vulnerability in Simple Terms
02Summary
The Drag and Drop Multiple File Upload for Contact Form 7 plugin allows unauthenticated attackers to upload files without proper validation. An attacker can upload malicious files—including executable code—to the server by sending a crafted request. This can lead to remote code execution, data theft, or site compromise. Update to a version newer than 1.3.9.7.
What an attacker can do
03Attacker Capabilities
Upload malicious files to the server and execute arbitrary code on the site.
Potential impact on your site
04Site Impact
Attackers can run code on your site, steal data, or take full control without needing a user account.
Conditions required to exploit
05Prerequisites
Network access only; no authentication or user interaction required.
Key dates
06Disclosure timeline
April 17, 2026
CVE published
May 27, 2026
Record updated
