CVE-2026-97291 in Schema & Structured Data for WP & AMP Plugin
Summary
by MITRE • 09/30/2026
Contributor PHP Object Injection in Schema & Structured Data for WP & AMP <= 1.66 versions.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified as Contributor PHP Object Injection within the Schema and Structured Data plugin for WordPress, specifically affecting versions up to 1.66, represents a critical security flaw rooted in improper input validation and unsafe deserialization practices. This type of attack vector allows an attacker with contributor-level or lower privileges on a compromised WordPress installation to manipulate internal application states by injecting malicious PHP objects into the system's data streams. The core technical issue lies in the plugin's handling of user-supplied data, where inputs are passed directly to functions that perform unserialization without adequate sanitization or type checking. In many modern web applications and CMS plugins, serialized strings are used for configuration storage, caching mechanisms, or passing complex state between different parts of the application. When these values originate from users with write access but lack rigorous validation against a whitelist of expected classes, an attacker can craft specific payloads that exploit existing autoloaded classes within the WordPress core or other installed plugins to execute arbitrary code during the deserialization process.
From a technical perspective, this vulnerability falls under the category of CWE-502, which denotes Deserialization of Untrusted Data. The exploitation mechanism typically involves constructing a serialized PHP object where the class name and its properties are manipulated to trigger magic methods such as __wakeup(), __destruct(), or __toString(). These methods often contain logic that interacts with file systems, database queries, or system commands. By leveraging these built-in functions of widely used classes like WP_Error or custom plugin objects, an attacker can achieve Remote Code Execution (RCE) without needing to upload a malicious script directly to the server's web root. This bypasses many traditional security controls because the execution occurs within the context of the PHP interpreter running under the web server user privileges, effectively granting the attacker full control over the underlying operating system depending on the configuration and permissions of that service account.
The operational impact of this vulnerability is severe, as it allows for a complete compromise of the affected WordPress site. An attacker can use this entry point to exfiltrate sensitive database contents including user credentials, personal data, and proprietary business information stored in the CMS. Furthermore, the compromised server can be turned into a pivot point for lateral movement within an organization's network infrastructure or used to distribute malware to visitors through drive-by download attacks. The presence of such vulnerabilities significantly degrades trust in the platform and exposes organizations to regulatory penalties under frameworks like GDPR or HIPAA if personal data is breached. Additionally, attackers may install persistent backdoors that survive plugin updates or site migrations, leading to long-term unauthorized access and potential botnet recruitment for distributed denial-of-service attacks.
Mitigation strategies must address both immediate remediation and long-term security hygiene. The primary and most effective solution is to upgrade the Schema & Structured Data plugin to version 1.67 or later, where developers have presumably patched the input validation logic and restricted deserialization operations to trusted sources only. For organizations unable to update immediately due to compatibility constraints, disabling PHP object serialization for untrusted inputs via server-side configuration changes can provide a temporary buffer, although this is not always feasible in shared hosting environments. Implementing strict Content Security Policies (CSP) and Web Application Firewalls (WAF) rules that detect patterns associated with serialized payloads or known exploit signatures related to WP_Error class manipulation can also help mitigate active exploitation attempts.
From an industry standard alignment perspective, this vulnerability maps directly to MITRE ATT&CK technique T1059, specifically Command and Scripting Interpreter sub-techniques such as PHP (T1059.007). The attack lifecycle involves Initial Access through low-privilege user accounts, followed by Execution via the deserialization flaw, and potentially Persistence if backdoors are installed. Security teams should audit their WordPress installations for any plugins that handle serialized data from user inputs, ensuring that only whitelisted classes are allowed to be instantiated during unserialization processes. Regular vulnerability scanning using tools configured to detect PHP object injection patterns is essential for maintaining a secure posture in environments running legacy or unmaintained plugin versions. Ultimately, adhering to the principle of least privilege and enforcing strict input validation protocols across all CMS components remains the most robust defense against this class of vulnerabilities.