Contact Form 7 <= 5.8.3 - Authenticated (Editor+) Arbitrary File Upload

The Contact Form 7 plugin for WordPress is vulnerable to arbitrary file uploads due to insufficient file type validation in the 'validate' function and insufficient blocklisting on the 'wpcf7_antiscript_file_name' function in versions up to, and including, 5.8.3. This makes it possible for authenticated attackers with editor-level capabilities or above to upload arbitrary files on the affected site's server, but due to the htaccess configuration, remote code cannot be executed in most cases. By default, the file will be deleted from the server immediately. However, in some cases, other plugins may make it possible for the file to live on the server longer. This can make remote code execution possible when combined with another vulnerability, such as local file inclusion.

An attacker needs Editor access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: Contact Form 7 5.8.4 closes this, and updating the plugin is the step that ends it.

• Firewall
• Scanner
• Alerts