CVE-2026-86407 in User Registration & Membership Plugin
Summary
by MITRE • 09/13/2026
The User Registration & Membership WordPress plugin before 5.2.8 does not verify that the visitor requesting its membership confirmation page owns the account named in the request, nor that any registration or purchase has taken place, allowing unauthenticated users to retrieve another user's email address, profile fields, role and membership order details. Exploitation requires the site owner to have added a user smart tag to that page's configurable message, which the shipped default does not contain.
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Analysis
by VulDB Data Team • 09/13/2026
The vulnerability identified in versions of the User Registration & Membership WordPress plugin prior to 5.2.8 represents a critical failure in access control and data validation mechanisms. This flaw allows unauthenticated attackers to retrieve sensitive personal information belonging to other users, including email addresses, profile fields, user roles, and membership order details. The core technical issue stems from the application's inability to verify that the visitor requesting the membership confirmation page actually owns the account referenced in the request parameters. Furthermore, the system fails to validate whether a legitimate registration or purchase transaction has occurred for the specified account before rendering the associated data. This lack of server-side validation creates an insecure direct object reference scenario where internal identifiers can be manipulated by external actors to access resources they are not authorized to view.
From a technical perspective, this vulnerability is classified under CWE-284, which covers Improper Access Control, and specifically aligns with the concept of Insecure Direct Object References (IDOR) as defined in CWE-639. The exploitation vector relies on the attacker manipulating input parameters that point to specific user records or membership instances within the database. Because the plugin does not enforce strict ownership checks against the session state or authenticated identity, it assumes that any request for a confirmation page is legitimate if the structural format of the request is correct. This architectural oversight permits automated scripts to iterate through potential user identifiers and harvest data systematically without requiring valid credentials or prior interaction with the site's registration flow.
The operational impact of this vulnerability extends beyond simple information disclosure. By exposing email addresses, profile fields, and membership details, attackers can facilitate targeted phishing campaigns, social engineering attacks, and credential stuffing attempts against high-value targets such as administrators or premium members. The exposure of user roles is particularly dangerous as it allows adversaries to map out the administrative structure of a WordPress installation, identifying which accounts possess elevated privileges for subsequent privilege escalation attacks. Additionally, knowledge of membership order details can reveal financial information or subscription statuses that may be leveraged in extortion schemes or further reconnaissance activities against the organization hosting the website.
It is important to note that exploitation of this vulnerability requires specific configuration conditions on the target WordPress site. The attacker must have a user smart tag present within the configurable message template of the membership confirmation page. This smart tag acts as the mechanism through which personal data is rendered into the HTML response. In many default installations, this feature may not be enabled or configured with such tags by default, meaning that while the code path exists and contains the flaw, it remains latent until an administrator explicitly configures the plugin to display user-specific information on that page. This dependency does not mitigate the severity of the underlying design flaw but rather limits its immediate exploitability in unmodified environments.
To remediate this vulnerability, site administrators should immediately upgrade the User Registration & Membership WordPress plugin to version 5.2.8 or later, where these access control checks have been implemented. For sites that cannot update immediately due to compatibility constraints, mitigation strategies include disabling the membership confirmation page feature if it is not actively used for business operations. Alternatively, administrators can remove any user smart tags from the configurable message templates associated with this page, thereby preventing the rendering of sensitive data even if an attacker successfully manipulates the request parameters. Implementing these controls ensures that personal identifiable information remains protected against unauthorized retrieval attempts and aligns security practices with industry standards for web application protection.