CVE-2026-25445: WishList Member X Object Injection Flaw

CVE-2026-25445 Overview

CVE-2026-25445 is a Deserialization of Untrusted Data vulnerability affecting the WishList Member X plugin for WordPress. This security flaw allows attackers to perform PHP Object Injection attacks against vulnerable WordPress installations running the affected plugin versions through version 3.29.0.

Critical Impact

Successful exploitation of this PHP Object Injection vulnerability could allow authenticated attackers with low privileges to execute arbitrary code, manipulate application data, or escalate privileges on affected WordPress sites.

Affected Products

• WishList Member X plugin for WordPress from n/a through version 3.29.0

Discovery Timeline

• 2026-03-19 - CVE CVE-2026-25445 published to NVD
• 2026-03-19 - Last updated in NVD database

Technical Details for CVE-2026-25445

Vulnerability Analysis

This vulnerability stems from improper handling of serialized data within the WishList Member X WordPress plugin. When the application deserializes user-controllable input without adequate validation, it creates an opportunity for attackers to inject malicious PHP objects. These objects can trigger dangerous operations when the application processes the crafted serialized data.

The vulnerability is classified under CWE-502 (Deserialization of Untrusted Data), which occurs when an application deserializes data from untrusted sources without proper verification. In PHP applications like WordPress plugins, this typically manifests when unserialize() is called on user-supplied input, allowing attackers to instantiate arbitrary objects with controlled properties.

The attack requires network access and low-level authentication to the WordPress site, but does not require user interaction to exploit. Successful exploitation can lead to complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of this vulnerability is the insecure deserialization of user-supplied data within the WishList Member X plugin. The application accepts serialized PHP objects from user input and passes them to PHP's native deserialization functions without implementing proper input validation or type checking. This allows attackers to craft malicious serialized payloads that, when deserialized, instantiate arbitrary PHP objects with attacker-controlled properties.

Attack Vector

The attack is conducted over the network and requires low-privilege authentication to the WordPress site. An attacker can exploit this vulnerability by crafting a malicious serialized PHP object and submitting it through a vulnerable endpoint in the WishList Member X plugin. When the application deserializes this payload, it instantiates the attacker's objects, potentially triggering magic methods like __wakeup(), __destruct(), or __toString() that can be chained to achieve code execution.

The exploitation typically involves identifying Property Oriented Programming (POP) chains within the WordPress ecosystem or the plugin itself. These chains allow attackers to leverage existing class methods to perform malicious actions such as file operations, database queries, or command execution. For detailed technical information, refer to the Patchstack Vulnerability Analysis.

Detection Methods for CVE-2026-25445

Indicators of Compromise

• Unusual serialized data in HTTP request parameters, particularly containing PHP object notation such as O: followed by class names
• Unexpected file system modifications in the WordPress installation directory
• Suspicious outbound network connections from the web server
• New or modified files in plugin directories that were not part of legitimate updates

Detection Strategies

• Monitor web application firewall (WAF) logs for requests containing serialized PHP objects in POST data or URL parameters
• Implement application-level logging to capture deserialization events and flag suspicious object instantiations
• Use WordPress security plugins to scan for known vulnerable plugin versions
• Deploy network intrusion detection rules to identify PHP object injection attack patterns

Monitoring Recommendations

• Enable verbose logging on the WordPress installation to capture detailed request information
• Configure alerts for new user account creations or privilege escalations
• Monitor file integrity of the WordPress core, themes, and plugins directories
• Review server access logs for repeated requests to plugin endpoints with unusual payload sizes

How to Mitigate CVE-2026-25445

Immediate Actions Required

• Update the WishList Member X plugin to a version newer than 3.29.0 that addresses this vulnerability
• Audit WordPress user accounts for unauthorized privilege escalations or suspicious new accounts
• Review server logs for evidence of exploitation attempts targeting this vulnerability
• Implement Web Application Firewall (WAF) rules to block serialized PHP objects in user input

Patch Information

The vulnerability affects WishList Member X versions through 3.29.0. Organizations should update to the latest available version that contains the security fix. For additional details and patch information, consult the Patchstack Vulnerability Analysis.

Workarounds

• If immediate patching is not possible, temporarily disable the WishList Member X plugin until the update can be applied
• Implement input validation at the web server or WAF level to reject requests containing serialized PHP data
• Restrict access to the WordPress admin panel to trusted IP addresses only
• Consider placing the site in maintenance mode if active exploitation is suspected

# Example WAF rule to block PHP serialized objects (ModSecurity)
SecRule REQUEST_BODY "@rx O:\d+:\"[^\"]+\":\d+:{" \
    "id:100001,\
    phase:2,\
    deny,\
    status:403,\
    log,\
    msg:'PHP Object Injection Attempt Blocked',\
    tag:'application-multi',\
    tag:'language-php',\
    tag:'attack-injection-php'"