CVE-2025-54693: Form Block File Upload RCE Vulnerability

CVE-2025-54693 Overview

CVE-2025-54693 is an unrestricted file upload vulnerability (CWE-434) in the epiphyt Form Block WordPress plugin that allows attackers to upload a web shell to a web server. This vulnerability enables remote attackers to upload malicious files with dangerous types, potentially leading to complete server compromise through arbitrary code execution.

Critical Impact

Attackers can exploit this vulnerability to upload web shells, achieving remote code execution on WordPress servers running vulnerable versions of the Form Block plugin (versions through 1.5.5).

Affected Products

• epiphyt Form Block plugin versions through 1.5.5
• WordPress installations using vulnerable Form Block plugin versions
• Web servers hosting affected WordPress sites

Discovery Timeline

• August 14, 2025 - CVE-2025-54693 published to NVD
• August 14, 2025 - Last updated in NVD database

Technical Details for CVE-2025-54693

Vulnerability Analysis

This vulnerability stems from insufficient file type validation in the Form Block plugin's file upload functionality. The plugin fails to properly restrict or validate the types of files that can be uploaded through forms created with the block editor. Without proper validation of file extensions, MIME types, or file content, attackers can bypass any client-side restrictions and upload executable files such as PHP web shells directly to the web server.

Once a web shell is successfully uploaded, the attacker can access it via a direct URL request, effectively gaining arbitrary code execution capabilities on the server. This allows for complete compromise of the WordPress installation and potentially the underlying server infrastructure.

Root Cause

The root cause is improper input validation on file uploads within the Form Block plugin. The plugin does not implement adequate server-side controls to verify that uploaded files are of safe, expected types. This lack of validation allows dangerous file types (such as .php, .phtml, or other executable scripts) to be uploaded and stored in publicly accessible directories on the web server.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a WordPress site using the vulnerable Form Block plugin
2. Locating a form that includes file upload functionality
3. Crafting a malicious PHP web shell file
4. Submitting the form with the web shell as the uploaded file
5. Accessing the uploaded file directly via URL to execute commands

The vulnerability allows attackers to bypass file type restrictions and upload arbitrary files. Due to the network-accessible nature of this attack, no prior authentication is required, making it particularly dangerous for public-facing WordPress sites.

Detection Methods for CVE-2025-54693

Indicators of Compromise

• Presence of unexpected PHP files in WordPress upload directories (e.g., wp-content/uploads/)
• Web server access logs showing requests to suspicious file paths with PHP extensions in upload directories
• Unusual outbound network connections from the web server
• New or modified PHP files with obfuscated code or common web shell signatures
• Unexpected process execution or system commands originating from web server processes

Detection Strategies

• Implement file integrity monitoring (FIM) on WordPress directories, particularly wp-content/uploads/
• Monitor web server logs for POST requests to form endpoints followed by GET requests to newly created files
• Deploy web application firewalls (WAF) with rules to detect web shell upload attempts
• Scan upload directories regularly for files with executable extensions that should not be present

Monitoring Recommendations

• Enable detailed logging for file upload activities in WordPress
• Configure alerts for new executable files appearing in upload directories
• Monitor for anomalous HTTP request patterns indicative of web shell interaction
• Implement network monitoring to detect command-and-control communications from compromised servers

How to Mitigate CVE-2025-54693

Immediate Actions Required

• Update the Form Block plugin to a patched version as soon as one becomes available
• Audit existing upload directories for suspicious files and remove any unauthorized content
• Temporarily disable file upload functionality in forms if an immediate patch is unavailable
• Implement server-side file type validation and whitelist only safe file extensions
• Consider temporarily deactivating the Form Block plugin until a security update is released

Patch Information

Refer to the Patchstack WordPress Vulnerability Report for the latest patch information and updates from the plugin vendor. Monitor the WordPress plugin repository for updated versions of Form Block that address this vulnerability.

Workarounds

• Configure web server to prevent execution of PHP files in upload directories using .htaccess rules
• Implement additional file validation at the server level to reject dangerous file types
• Use a web application firewall to block requests containing web shell signatures
• Restrict upload directory permissions to prevent execution of uploaded files

# Apache .htaccess configuration to prevent PHP execution in uploads directory
# Add to wp-content/uploads/.htaccess
<FilesMatch "\.(?:php|phtml|php3|php4|php5|phps)$">
    Require all denied
</FilesMatch>

# Alternative: Disable PHP engine entirely in directory
php_flag engine off