CVE-2026-105436 in Child Plugin
Summary
by MITRE • 10/08/2026
Deserialization of Untrusted Data vulnerability in MainWP MainWP Child mainwp-child allows Object Injection.This issue affects MainWP Child: from n/a through 6.2.1.
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Analysis
by VulDB Data Team • 10/08/2026
The identified vulnerability represents a critical security flaw within the MainWP Child plugin, specifically affecting versions ranging from initial releases up to version 6.2.1. This issue is classified as an insecure deserialization of untrusted data, which fundamentally allows for object injection attacks against the targeted WordPress environment. In modern web application architecture, particularly those built on PHP frameworks like WordPress, serialization is frequently used to store complex data structures in a format that can be easily saved or transmitted. However, when these serialized objects are reconstructed from user-controlled input without adequate validation or sanitization, it creates an opening for malicious actors to manipulate the internal state of the application.
The technical mechanism behind this vulnerability relies on PHP's unserialize function being exposed to external inputs such as POST parameters, cookies, or headers that have not been properly validated. An attacker can craft a specially formatted serialized string containing a malicious object with properties designed to exploit existing classes within the WordPress core or other installed plugins. When the vulnerable code processes this input, it instantiates these objects, potentially triggering magic methods like __wakeup or __destruct which may execute arbitrary commands, access sensitive files, or modify database records. This process bypasses standard authentication and authorization checks if the deserialization occurs in a context where session validation is insufficient or absent for specific endpoints.
From an operational perspective, this vulnerability poses severe risks to website integrity and data confidentiality. Successful exploitation can lead to full remote code execution on the server hosting the WordPress instance. Attackers may use this access to deface websites, install web shells for persistent backdoor access, exfiltrate sensitive customer or administrative data, or pivot further into internal networks if the server is part of a larger infrastructure. Given that MainWP is used by agencies and freelancers to manage multiple client sites, compromising one instance through this vulnerability could potentially lead to widespread compromise across all managed websites if proper isolation measures are not in place. The impact extends beyond technical disruption to include significant reputational damage and potential regulatory penalties under data protection laws like GDPR or CCPA due to the exposure of personal information.
This flaw aligns with CWE-502, which describes deserialization of untrusted data as a weakness where an application reconstructs objects from input without ensuring that the content is trustworthy. Furthermore, in terms of offensive security frameworks such as MITRE ATT&CK, this vulnerability facilitates techniques related to Command and Control via Application Layer Protocol or Initial Access through Exploitation of Remote Services. The ability to inject arbitrary PHP objects effectively grants the attacker a foothold equivalent to direct code execution, allowing them to bypass many traditional input validation controls that do not account for serialized payload structures.
To mitigate this risk, immediate action is required by upgrading MainWP Child to version 6.2.2 or later where the vulnerability has been patched. Administrators should also implement strict allowlisting of expected data types and values before any deserialization occurs, avoiding the use of unserialize on user-supplied input entirely if possible. Utilizing JSON for data interchange instead of PHP serialization is a recommended best practice as it does not support object instantiation in the same dangerous manner. Additionally, deploying Web Application Firewalls with rules specifically tuned to detect serialized payload patterns can provide an additional layer of defense against exploitation attempts while patching efforts are underway. Regular security audits and code reviews focusing on data handling routines will help prevent similar vulnerabilities from being introduced in future updates or custom integrations.