CVE-2025-68853: Kleor Contact Manager Object Injection

CVE-2025-68853 Overview

CVE-2025-68853 is a PHP Object Injection vulnerability resulting from insecure deserialization in the Kleor Contact Manager WordPress plugin. The vulnerability allows authenticated attackers to inject arbitrary PHP objects through untrusted data deserialization, potentially leading to remote code execution, data theft, or complete site compromise depending on available gadget chains in the WordPress environment.

Critical Impact

Authenticated attackers can exploit insecure deserialization to inject malicious PHP objects, potentially achieving remote code execution or full WordPress site compromise through object injection attacks.

Affected Products

• Kleor Contact Manager WordPress Plugin version 9.1.1 and earlier
• WordPress sites running vulnerable Contact Manager plugin versions
• All Contact Manager installations from initial release through version 9.1.1

Discovery Timeline

• 2026-02-20 - CVE CVE-2025-68853 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2025-68853

Vulnerability Analysis

This vulnerability stems from CWE-502: Deserialization of Untrusted Data, a critical class of vulnerabilities that occurs when an application deserializes user-controllable data without proper validation. In the context of PHP applications like WordPress plugins, this typically involves the unsafe use of the unserialize() function on attacker-controlled input.

PHP Object Injection vulnerabilities are particularly dangerous in WordPress environments due to the extensive class hierarchy available from WordPress core, themes, and other plugins. When malicious serialized data is passed to unserialize(), an attacker can instantiate arbitrary PHP objects with controlled properties. If a suitable "gadget chain" exists—a sequence of classes with magic methods like __wakeup(), __destruct(), or __toString() that perform dangerous operations—the attacker can achieve significant impact including arbitrary code execution, file operations, or database manipulation.

The Kleor Contact Manager plugin fails to properly validate or sanitize serialized data before deserialization, creating this attack surface. The vulnerability requires low-privilege authentication to exploit, but once authenticated, an attacker can leverage the object injection to escalate privileges or execute arbitrary code.

Root Cause

The root cause is the improper use of PHP's unserialize() function on user-supplied input without adequate validation. The Contact Manager plugin processes serialized data in a manner that allows attackers to inject crafted PHP objects. Secure alternatives include using JSON encoding/decoding for data interchange or implementing strict allowlists for classes that can be unserialized using PHP 7+'s allowed_classes option.

Attack Vector

The attack is network-based and requires authenticated access to the WordPress site, though only low-level privileges are needed. An attacker would craft a malicious serialized PHP object payload and submit it through the vulnerable Contact Manager functionality. The exploitation flow typically involves:

1. Identifying the deserialization entry point in the Contact Manager plugin
2. Enumerating available PHP classes in the WordPress environment for potential gadget chains
3. Crafting a serialized payload that chains together class instantiations and magic method calls
4. Submitting the payload through the vulnerable parameter
5. Achieving code execution or other impact when the object is deserialized

For detailed technical analysis of this vulnerability, refer to the Patchstack WordPress Vulnerability Database.

Detection Methods for CVE-2025-68853

Indicators of Compromise

• Unusual serialized PHP object strings containing class names in HTTP request parameters or POST data
• Presence of malformed or unexpected class instantiations in WordPress debug logs
• Suspicious PHP serialized data patterns in web access logs (e.g., O:4:"ClassName"...)
• Unexpected file system changes or new files created in WordPress directories

Detection Strategies

• Monitor web application firewall logs for serialized PHP object patterns in request parameters
• Implement WordPress security plugins that detect and block serialization attacks
• Review web server access logs for requests containing suspicious serialized data to Contact Manager endpoints
• Deploy runtime application self-protection (RASP) solutions that can detect deserialization attacks

Monitoring Recommendations

• Enable verbose logging for the WordPress application and review for deserialization-related errors
• Configure SentinelOne Singularity to monitor for suspicious PHP process behavior and file operations
• Set up alerts for unusual database queries or modifications originating from the Contact Manager plugin
• Monitor for new PHP files or modifications to existing files that could indicate successful exploitation

How to Mitigate CVE-2025-68853

Immediate Actions Required

• Update the Kleor Contact Manager plugin to the latest patched version immediately
• If no patch is available, consider deactivating and removing the Contact Manager plugin until a fix is released
• Audit WordPress user accounts and remove unnecessary authenticated users to reduce attack surface
• Implement a Web Application Firewall (WAF) rule to block serialized PHP object patterns in requests

Patch Information

Organizations should check the Patchstack advisory for the latest patch availability and version information. Upgrade Contact Manager to a version newer than 9.1.1 when available. If the plugin has been abandoned or no patch is forthcoming, consider migrating to an alternative contact management solution.

Workarounds

• Deactivate the Contact Manager plugin if it is not business-critical until a patch is available
• Implement strict input validation at the web server level using ModSecurity or similar WAF rules
• Restrict plugin access to only trusted administrator accounts and audit authentication logs
• Deploy SentinelOne Singularity endpoint protection to detect and block post-exploitation activities

# WordPress CLI commands to manage vulnerable plugin
# Check current Contact Manager version
wp plugin list --name=contact-manager --fields=name,version,status

# Deactivate vulnerable plugin as temporary mitigation
wp plugin deactivate contact-manager

# After patch release, update to latest version
wp plugin update contact-manager

# Verify updated version
wp plugin list --name=contact-manager --fields=name,version,update