CVE-2026-114451 in Membership Plugin
Summary
by MITRE • 11/15/2026
The Membership Plugin WordPress plugin before 4.0.6 does not perform any authorization or CSRF check before running a schema-altering database maintenance routine, allowing unauthenticated users to convert the Membership Plugin WordPress plugin before 4.0.6's own tables to a narrower character set, which irreversibly replaces every 4-byte character (such as emoji and some CJK characters) in the membership level, discount code and payment records with a question mark.
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Analysis
by VulDB Data Team • 11/15/2026
The vulnerability identified in Membership Plugin for WordPress prior to version 4.0.6 represents a critical failure in access control mechanisms within the plugin's administrative functionality. Specifically, the flaw resides in the execution of schema-altering database maintenance routines that are designed to optimize or modify table structures. These operations typically involve altering character sets and collations to ensure data integrity across different environments. However, the implementation fails to enforce any form of authorization check before initiating these destructive processes. This absence of validation allows unauthenticated actors to trigger administrative-level actions without possessing valid credentials or session tokens, effectively bypassing the fundamental security boundary that separates public-facing endpoints from privileged management interfaces.
From a technical perspective, this vulnerability is classified under CWE-269, which denotes Improper Privilege Control, and aligns with ATT&CK technique T1078, Valid Accounts, as it allows an attacker to perform actions reserved for administrators without valid authentication. The core of the issue lies in the lack of CSRF protection combined with missing role verification. In WordPress architecture, certain AJAX endpoints or admin-ajax calls are intended only for users with specific capabilities such as manage_options or edit_users. By omitting checks for these roles and failing to validate nonces or other anti-CSRF tokens, the plugin exposes its database modification logic to any remote user who can send a crafted HTTP request. This allows an attacker to manipulate the underlying MySQL schema of the membership tables directly through web requests.
The operational impact of this vulnerability is severe due to the irreversible nature of the character set conversion involved. The malicious actor can force the database to convert its tables from utf8mb4, which supports 4-byte characters including emojis and complex CJK scripts, to a narrower charset such as utf8 or latin1 that only supports up to 3 bytes per character. When this conversion occurs, any data stored using more than three bytes is irreversibly corrupted. In the context of a membership plugin, this results in the replacement of every multi-byte character within critical fields like membership level names, discount codes, and payment records with question marks or other placeholder symbols. This leads to immediate data loss for international users whose usernames or custom fields contain emojis or non-Latin characters, potentially causing significant disruption to business operations and customer experience.
Furthermore, the integrity of financial and access control data is compromised as discount codes may become unreadable or invalid, leading to revenue loss or unauthorized access if fallback mechanisms exist. The irreversible nature of this corruption means that standard backups taken after the vulnerability was exploited will also contain the corrupted data unless a pre-exploit backup exists. This highlights the importance of maintaining robust backup strategies and monitoring database integrity regularly.
Mitigation for this issue requires immediate action by site administrators to upgrade the Membership Plugin to version 4.0.6 or later, where these authorization checks have been implemented. Until an update is applied, temporary mitigations include restricting access to the WordPress admin-ajax.php endpoint via web application firewall rules that block unauthenticated POST requests targeting known vulnerable actions associated with this plugin. Additionally, implementing strict input validation and ensuring that all administrative functions require both valid authentication tokens and proper role verification can prevent similar vulnerabilities in other plugins or custom code. Regular security audits focusing on privilege escalation paths are recommended to identify and remediate such access control failures across the entire WordPress installation ecosystem.