CVE-2026-109699 in User Registration Plugin
Summary
by MITRE • 10/13/2026
Missing Authorization vulnerability in ThemeGrill User Registration user-registration allows Exploiting Incorrectly Configured Access Control Security Levels.This issue affects User Registration: from n/a through 5.2.8.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/13/2026
The identified security flaw represents a critical failure in access control mechanisms within the ThemeGrill User Registration plugin, specifically affecting versions ranging from an unspecified initial release up to version 5.2.8. This vulnerability is classified as Missing Authorization, which fundamentally indicates that the application fails to properly verify whether a user has the necessary permissions to perform specific actions or access certain resources. In the context of web applications and plugins like this one, such failures typically manifest when endpoints designed for administrative functions or sensitive data manipulation are accessible to unauthenticated users or those with lower privilege levels than required. The core technical flaw lies in the absence of robust server-side checks that validate user roles before processing requests, allowing attackers to bypass intended security boundaries through Incorrectly Configured Access Control Security Levels.
From a technical perspective, this vulnerability allows an attacker to interact with protected endpoints without valid authentication tokens or proper role verification. By manipulating HTTP parameters such as action IDs, nonce values, or direct URL paths associated with user management features, the malicious actor can execute operations that should be restricted to administrators or verified users. This could include creating new administrative accounts, modifying existing user profiles, changing password reset mechanisms, or accessing sensitive database records containing personal identifiable information of registered users. The lack of authorization checks means the application trusts client-supplied input regarding intent and privilege level rather than enforcing strict server-side policy enforcement, a common pitfall in legacy codebases that prioritize functionality over security rigor.
The operational impact of this vulnerability is severe, as it directly compromises the integrity and confidentiality of user data managed by the platform. Attackers can exploit these misconfigured access controls to escalate privileges within the application environment, potentially gaining full control over the WordPress installation if administrative capabilities are exposed. This leads to a complete compromise of the underlying website, enabling further attacks such as defacement, malware injection, or using the server for distributed denial-of-service activities and phishing campaigns against other users. Furthermore, because user registration plugins often handle sensitive personal data including email addresses, phone numbers, and potentially payment information if integrated with e-commerce modules, the exposure of this data violates privacy regulations like GDPR or CCPA and erodes trust in the service provider.
To mitigate these risks, immediate action is required to update the ThemeGrill User Registration plugin to a version newer than 5.2.8 where the authorization checks have been properly implemented and tested. Administrators should also audit their server configurations to ensure that sensitive administrative URLs are not directly accessible without proper authentication layers such as two-factor authentication or IP whitelisting for admin areas. Implementing Web Application Firewalls can provide an additional layer of defense by detecting and blocking requests that exhibit patterns typical of authorization bypass attempts, such as unusual parameter manipulation or repeated failed access attempts to restricted endpoints. Regular security audits and penetration testing focused on role-based access control are essential to identify similar gaps in other plugins or custom code within the ecosystem.
This vulnerability aligns with CWE-284 Improper Access Control, which covers scenarios where an actor is able to bypass intended restrictions by exploiting flaws in authorization logic rather than authentication mechanisms. It also maps closely to MITRE ATT&CK technique T1078 Valid Accounts, specifically the sub-technique of using default accounts or misconfigured permissions to gain unauthorized access. By addressing these specific control failures and adhering to secure coding standards that enforce least privilege principles, organizations can significantly reduce their attack surface and protect against exploitation of similar authorization flaws in future software updates.