CVE-2025-53299: ThemeMakers Visual Content Composer Flaw

CVE-2025-53299 Overview

A critical Deserialization of Untrusted Data vulnerability has been identified in ThemeMakers Visual Content Composer, a WordPress plugin. This vulnerability allows attackers to perform PHP Object Injection attacks against vulnerable WordPress installations. The flaw exists due to improper handling of serialized data, enabling unauthenticated attackers to inject arbitrary PHP objects into the application.

Critical Impact

Unauthenticated attackers can exploit this PHP Object Injection vulnerability to potentially achieve remote code execution, manipulate application data, or cause denial of service on affected WordPress installations.

Affected Products

• ThemeMakers Visual Content Composer versions through 1.5.8
• WordPress sites using the tmm_content_composer plugin

Discovery Timeline

• 2025-08-20 - CVE-2025-53299 published to NVD
• 2025-08-20 - Last updated in NVD database

Technical Details for CVE-2025-53299

Vulnerability Analysis

This vulnerability is classified as CWE-502 (Deserialization of Untrusted Data). PHP Object Injection occurs when user-controlled input is passed to the unserialize() function without proper validation or sanitization. In the context of the ThemeMakers Visual Content Composer plugin, the application processes serialized data from untrusted sources, allowing attackers to craft malicious serialized objects.

When the vulnerable unserialize() function processes attacker-controlled data, it can instantiate arbitrary PHP objects within the application. If suitable "gadget chains" exist within the application or its dependencies (classes with magic methods like __wakeup(), __destruct(), or __toString()), attackers can chain these methods to achieve various malicious outcomes including arbitrary file operations, database manipulation, or remote code execution.

The vulnerability is exploitable over the network without requiring authentication or user interaction, making it particularly dangerous for public-facing WordPress installations.

Root Cause

The root cause of this vulnerability is the use of PHP's unserialize() function on untrusted user input without proper validation. The plugin fails to verify the integrity and source of serialized data before deserialization, allowing attackers to inject arbitrary PHP objects. This is a common vulnerability pattern in PHP applications where developers use serialization for data storage or transfer without implementing proper security controls.

Attack Vector

The attack is network-based and can be executed remotely without authentication. Attackers can submit specially crafted serialized PHP objects through vulnerable input vectors in the plugin. Upon deserialization, the malicious objects are instantiated, and their magic methods are triggered automatically by the PHP runtime.

The exploitation process typically involves:

1. Identifying the vulnerable deserialization endpoint in the plugin
2. Analyzing available classes in WordPress and the plugin for exploitable gadget chains
3. Crafting a malicious serialized payload that leverages these gadget chains
4. Submitting the payload to trigger the unserialize() function
5. Achieving the desired impact through the triggered object methods

For detailed technical information about this vulnerability, refer to the Patchstack Vulnerability Advisory.

Detection Methods for CVE-2025-53299

Indicators of Compromise

• Unusual serialized data patterns in web server access logs containing PHP object syntax (e.g., O: followed by class names)
• Unexpected file system modifications in WordPress installation directories
• Anomalous PHP process behavior or unexpected child processes spawned by the web server
• Web application firewall alerts for serialized object injection attempts

Detection Strategies

• Monitor web application logs for requests containing serialized PHP object patterns targeting the Visual Content Composer plugin endpoints
• Implement intrusion detection rules to identify deserialization attack patterns in HTTP request bodies and parameters
• Deploy web application firewalls (WAF) with rules to detect and block PHP object injection payloads
• Review WordPress plugin activity logs for unauthorized actions originating from the Visual Content Composer plugin

Monitoring Recommendations

• Enable verbose logging for the WordPress installation and monitor for unusual plugin behavior
• Configure security information and event management (SIEM) systems to alert on PHP object injection indicators
• Regularly audit installed plugin versions and compare against known vulnerable releases
• Monitor outbound network connections from the web server for potential command and control communication

How to Mitigate CVE-2025-53299

Immediate Actions Required

• Immediately audit your WordPress installations for the ThemeMakers Visual Content Composer plugin
• Deactivate and remove the plugin if running version 1.5.8 or earlier until a patched version is available
• Review web server logs for any indicators of exploitation attempts
• Consider implementing temporary WAF rules to block serialized object injection patterns

Patch Information

Organizations using ThemeMakers Visual Content Composer should monitor the official plugin channels and the Patchstack Vulnerability Advisory for patch availability. Upgrade to a patched version immediately when released by the vendor.

Workarounds

• Disable or remove the ThemeMakers Visual Content Composer plugin until a security patch is available
• Implement WAF rules to block requests containing serialized PHP object patterns (e.g., blocking patterns matching O:[0-9]+:" in request bodies)
• Restrict access to WordPress admin panels and plugin functionality to trusted IP addresses where possible
• Consider using WordPress security plugins that provide virtual patching capabilities for known vulnerabilities

# WordPress CLI command to deactivate the vulnerable plugin
wp plugin deactivate tmm_content_composer --path=/var/www/html/wordpress

# Verify plugin is deactivated
wp plugin status tmm_content_composer --path=/var/www/html/wordpress