CVE-2026-32563 in Advanced Custom Post Type Plugin
Summary
by MITRE • 08/25/2026
Subscriber PHP Object Injection in ACPT (Pro) - Custom Post Types Plugin for WordPress <= 2.0.63 versions.
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Analysis
by VulDB Data Team • 08/25/2026
The vulnerability identified as a Subscriber PHP Object Injection within the ACPT Pro plugin, specifically affecting versions up to and including 2.0.63 of this popular WordPress extension for managing custom post types, represents a critical security flaw rooted in improper deserialization practices. This type of attack exploits the mechanism by which serialized data is converted back into executable objects without sufficient validation or sanitization of user-supplied input. In the context of web applications like WordPress, where plugins often handle complex state management and configuration storage through serialization, an attacker who can influence the content being unserialized gains a powerful vector for code execution. The flaw typically arises when functions such as unserialize are invoked on data that originates from or is influenced by user-controlled sources, such as HTTP request parameters, cookies, or stored database entries that have not been properly escaped before retrieval and subsequent processing.
From a technical perspective, this vulnerability aligns with CWE-502, which describes Deserialization of Untrusted Data. The core issue lies in the assumption that serialized data is safe to process simply because it was generated by the application itself or stored in a trusted location. However, if an attacker can manipulate the input stream before it reaches the deserialization function, they can inject malicious object graphs. When these objects are instantiated, their constructors and magic methods may execute arbitrary code within the context of the web server user account. This is particularly dangerous because PHP allows for polymorphic attacks where different classes define specific behaviors that an attacker can chain together to achieve remote code execution (RCE). The ACPT plugin likely processes custom post type configurations or metadata during page loads, and if any part of this process involves unserializing data derived from user input without rigorous validation, it creates a direct path for exploitation.
The operational impact of successfully exploiting this vulnerability is severe, potentially leading to complete compromise of the affected WordPress installation. An attacker could achieve Remote Code Execution with the privileges of the web server process, which typically has read and write access to all files within the website directory structure. This allows the adversary to upload backdoors, modify core application files, extract sensitive database information including user credentials and personal data, or pivot further into internal network infrastructure if the WordPress instance is accessible from there. Furthermore, because this vulnerability affects a widely used plugin for managing custom post types, it poses a significant risk to businesses relying on structured content management systems where integrity of data structures is paramount. The ability to inject arbitrary PHP objects means that standard security controls like input validation at the application level may be bypassed if they do not specifically address serialization boundaries.
This vulnerability maps directly to MITRE ATT&CK technique T1059, Command and Scripting Interpreter: PHP, as it enables the execution of arbitrary commands through PHP code injection via object instantiation. It also relates to T1190, Exploit Public-Facing Application, given that WordPress plugins are frequently exposed to public internet traffic where attackers actively scan for known vulnerabilities in popular software components. The exploitation does not necessarily require authentication if the vulnerable endpoint is accessible to subscribers or even anonymous users depending on how the plugin handles its internal logic and capability checks. Even with limited privileges such as Subscriber level access, which typically allows only basic content viewing and editing, the ability to trigger a PHP object injection can escalate privileges significantly due to the nature of server-side execution rather than client-side manipulation.
Mitigation strategies must prioritize immediate remediation through software updates. Administrators running ACPT Pro versions 2.0.63 or earlier should upgrade to the latest patched version where this deserialization flaw has been addressed by implementing strict type checking and whitelisting allowed classes during unserialization processes. If an update is not immediately available, temporary mitigations include disabling any functionality that allows user input to influence serialized data structures until a patch can be applied. Additionally, enabling PHP configuration settings such as disable_functions for dangerous functions like unserialize or exec can provide a layer of defense in depth, although this may impact legitimate plugin functionality and should be tested carefully in staging environments first. Regular security audits focusing on deserialization practices across all installed plugins are recommended to prevent similar vulnerabilities from being introduced through other extensions that might share the same architectural patterns.