CVE-2026-94076 in SEO Plugin
Summary
by MITRE • 09/30/2026
Contributor PHP Object Injection in SEO Plugin by Squirrly SEO <= 14.2.5 versions.
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified as Contributor PHP Object Injection within the Squirrly SEO plugin, affecting versions up to and including 14.2.5, represents a critical security flaw rooted in improper handling of user-supplied input during object serialization processes. This type of attack vector exploits the inherent dangers associated with deserializing untrusted data in PHP applications. When an application accepts serialized objects from external sources without rigorous validation or sanitization, it creates an opportunity for attackers to inject malicious payloads that manipulate internal program flow. In this specific instance, the flaw allows a contributor-level user, who typically possesses limited privileges such as creating and editing posts, to execute arbitrary code on the server by leveraging the deserialization mechanism within the plugin's functionality.
The technical core of this vulnerability lies in how the Squirrly SEO plugin processes data submitted through its interface. PHP applications often use serialization to store complex data structures or pass them between functions. However, if these serialized strings are derived directly from user input without ensuring that only expected object types and properties are instantiated, an attacker can craft a specially formatted string containing references to other classes within the application or even external libraries. Upon deserialization, PHP attempts to instantiate these objects, potentially triggering magic methods such as __wakeup(), __destruct(), or __toString(). These methods often contain logic for cleanup, resource management, or output generation, which an attacker can hijack to perform unintended actions, including reading sensitive files, executing system commands, or escalating privileges within the application context.
From a classification perspective, this vulnerability aligns with CWE-502, Deserialization of Untrusted Data, and is closely related to CWE-94, Improper Control of Generation of Code (Code Injection). The operational impact is severe because it bypasses standard authentication checks by exploiting lower-level user roles that are often assumed to be safe. A contributor gaining the ability to execute arbitrary PHP code effectively compromises the entire web application environment. This can lead to full server compromise, allowing attackers to install backdoors, exfiltrate database contents containing customer or administrative data, deface websites, or use the compromised server as a pivot point for further attacks against internal networks. The presence of this flaw undermines the principle of least privilege and demonstrates how seemingly minor role-based vulnerabilities can escalate into critical system-level breaches when combined with dangerous language features like dynamic deserialization.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The most effective solution is to upgrade the Squirrly SEO plugin to a version where this vulnerability has been patched by the vendor, ensuring that input validation mechanisms are strengthened and unsafe deserialization calls are removed or secured with whitelisting of allowed classes. In environments where an immediate update is not feasible, administrators should consider restricting file permissions on critical directories such as wp-content/uploads and plugins to prevent write access from web server processes unless absolutely necessary. Additionally, implementing a Web Application Firewall (WAF) can help detect and block patterns associated with PHP object injection attempts by analyzing request payloads for suspicious serialized data structures or known exploit signatures.
To enhance defense-in-depth, developers should avoid using native PHP serialization functions like serialize() and unserialize() on user-controlled input entirely. Instead, they should adopt safer alternatives such as JSON encoding and decoding, which do not support arbitrary class instantiation and thus neutralize the primary mechanism of this attack vector. Furthermore, enabling strict error reporting during development phases can help identify instances where unvalidated data is passed to deserialization functions before deployment. Regular security audits focusing on input validation and output encoding practices are essential for maintaining robust application integrity against evolving threats like PHP Object Injection.