CVE-2026-25450 in User Registration Plugin
Summary
by MITRE • 10/29/2026
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 5.3.0.
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Analysis
by VulDB Data Team • 10/29/2026
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 5.3.0. 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 flaws typically arise when endpoints or functions do not adequately check the session state or role capabilities before executing sensitive logic. This oversight allows attackers to bypass intended security boundaries by directly interacting with internal application interfaces that were designed for privileged users only.
From a technical perspective, the core issue lies in the incorrect configuration of access control levels. The software does not enforce strict separation between administrative functions and those available to standard or unauthenticated users. Consequently, an attacker can manipulate HTTP requests to trigger actions such as modifying user roles, creating new administrator accounts, or altering plugin settings without providing valid credentials for these privileged operations. This type of vulnerability is often exploited through direct object references or by manipulating form parameters that are not properly validated on the server side. The lack of robust authorization checks means that any request reaching the vulnerable code path can be executed regardless of the requester's actual identity or privilege level, effectively neutralizing authentication measures if they rely solely on session presence rather than explicit permission verification for each action.
The operational impact of this vulnerability is severe, as it directly compromises the integrity and confidentiality of the hosted website. An attacker with basic knowledge of web technologies can exploit this flaw to gain unauthorized administrative access. This level of compromise allows the adversary to install malicious plugins, inject code into themes or posts, steal sensitive user data including email addresses and hashed passwords, and potentially use the compromised server as a pivot point for further attacks against other systems on the network. The ability to escalate privileges from a low-privilege account to an administrator role is particularly dangerous because it grants full control over the application environment, leading to potential defacement, data breaches, and significant reputational damage for the organization hosting the site.
This vulnerability aligns with CWE-284, which describes Improper Access Control, specifically highlighting scenarios where access controls are not enforced correctly or are bypassed due to misconfiguration. Furthermore, in terms of offensive security frameworks such as MITRE ATT&CK, this flaw facilitates techniques related to Privilege Escalation and Account Manipulation. Attackers can leverage these capabilities to establish persistence within the system by creating backdoor accounts that survive password changes or plugin updates. The exploitation path often involves crafting specific HTTP requests with modified parameters to trigger administrative functions, a technique commonly associated with Broken Access Control attacks in web application security assessments.
To mitigate this risk, immediate action is required from site administrators and developers. The primary recommendation is to update the ThemeGrill User Registration plugin to version 5.3.1 or any later release where these authorization checks have been properly implemented and tested. If updating is not immediately feasible due to compatibility constraints with other plugins or themes, temporary mitigations should be considered. These may include restricting access to the WordPress admin area via IP whitelisting if possible, although this does not fully address API-level vulnerabilities. Additionally, implementing a Web Application Firewall can help detect and block suspicious request patterns associated with privilege escalation attempts, such as unusual POST requests targeting administrative endpoints from non-administrator sessions. Regular security audits and penetration testing are also advised to identify similar misconfigurations in other parts of the application stack before they can be exploited by malicious actors.