CVE-2026-4136 in Membership Plugin
Summary
by MITRE • 03/20/2026
The Membership Plugin – Restrict Content plugin for WordPress is vulnerable to Unvalidated Redirect in all versions up to, and including, 3.2.24. This is due to insufficient validation on the redirect url supplied via the 'rcp_redirect' parameter. This makes it possible for unauthenticated attackers to redirect users with the password reset email to potentially malicious sites if they can successfully trick them into performing an action.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/23/2026
The membership plugin restrict content for wordpress represents a widely used solution for managing user access and content restriction on wordpress websites. This plugin enables site administrators to create membership levels, control content access, and manage user authentication processes. The vulnerability identified in versions up to and including 3.2.24 affects the plugin's handling of redirect parameters during password reset operations. The issue stems from inadequate input validation mechanisms that fail to properly sanitize or verify the destination URLs specified in the rcp_redirect parameter. This flaw creates a significant security risk for wordpress installations that rely on this plugin for user management and authentication processes.
The technical implementation of this vulnerability involves the plugin's failure to validate redirect URLs before processing user requests. When users initiate password reset operations, the plugin accepts a redirect parameter that should guide users to a specific destination after authentication. However, the plugin does not properly validate or sanitize this parameter, allowing attackers to inject malicious URLs. The vulnerability specifically affects the password reset functionality where the rcp_redirect parameter is processed without sufficient security checks. This unvalidated redirect behavior creates opportunities for attackers to manipulate user navigation and potentially redirect them to phishing sites or malicious domains. The flaw operates at the input validation layer where proper sanitization should occur but fails to prevent the injection of arbitrary URLs.
The operational impact of this vulnerability extends beyond simple redirection attacks and presents serious risks to user security and trust. An attacker could exploit this vulnerability by crafting malicious links that appear legitimate but redirect users to phishing sites designed to capture credentials or personal information. The vulnerability affects unauthenticated attackers who can leverage this flaw without requiring administrative access or user credentials. This creates a significant threat vector where attackers can manipulate user workflows during password reset operations, potentially leading to credential theft, data breaches, or further exploitation of compromised accounts. The impact is particularly concerning given that password reset functionality is a critical user access point that users frequently interact with, making it an attractive target for social engineering attacks.
Organizations utilizing the restrict content plugin should implement immediate mitigation strategies to protect their users and systems. The primary recommendation involves upgrading to the latest version of the plugin where this vulnerability has been addressed through proper input validation and sanitization of redirect parameters. Security patches should be applied promptly to prevent exploitation of this vulnerability. Additionally, administrators should consider implementing additional security measures such as monitoring redirect behavior in web application firewalls and implementing strict validation rules for all redirect parameters. Network-level protections can include filtering malicious domains and monitoring for suspicious redirect patterns in authentication flows. The vulnerability aligns with CWE-601 open redirect vulnerability classification and represents a potential entry point for attackers following ATT&CK technique T1566.001 credential access through social engineering. Regular security audits of wordpress plugins and their configurations should be conducted to identify similar validation flaws in other components of the web application stack.