CVE-2026-4327 in The Welcomizer Plugin
Summary
by MITRE • 09/19/2026
The The Welcomizer plugin for WordPress is vulnerable to Remote Code Execution in all versions up to and including 2.8.1. This is due to missing authorization checks on the twiz_ajax_callback AJAX action's 'savesection' handler combined with the use of eval() to execute user-supplied 'custom logic' code on the frontend. The AJAX handler at twiz-ajax.php verifies a nonce but performs no current_user_can() capability check for the ACTION_SAVE_SECTION case. Furthermore, the nonce is exposed to any authenticated user through the directly-accessible twiz-ajax.js.php file which loads WordPress and outputs the nonce. This makes it possible for authenticated attackers, with Subscriber-level access and above, to inject arbitrary PHP code via the twiz_custom_logic POST parameter when saving a section with output choice 'twiz_logic_output'.
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Analysis
by VulDB Data Team • 09/19/2026
The Welcomizer plugin for WordPress contains a critical Remote Code Execution vulnerability affecting all versions up to and including 2.8.1. This flaw stems from insufficient authorization checks on the twiz_ajax_callback AJAX action, specifically within its savesection handler. The core technical issue involves the combination of missing capability verification and the unsafe execution of user-supplied input via PHP's eval function. An attacker can exploit this by injecting arbitrary PHP code through the twiz_custom_logic POST parameter when saving a section with an output choice set to twiz_logic_output. This vulnerability allows authenticated attackers, starting from Subscriber-level access or higher, to execute malicious scripts on the server side, potentially leading full compromise of the WordPress installation and underlying infrastructure.
From a technical perspective, the vulnerability arises because the AJAX handler located at twiz-ajax.php performs only a nonce verification but fails to implement any current_user_can capability check for the ACTION_SAVE_SECTION case. While nonces are designed to prevent Cross-Site Request Forgery attacks by ensuring that requests originate from legitimate forms within the application session, they do not inherently validate user permissions or roles. In this specific implementation, the nonce is exposed to all authenticated users through a directly accessible file named twiz-ajax.js.php. This script loads WordPress and outputs the nonce value, effectively allowing any logged-in user with minimal privileges to obtain valid authentication tokens required for subsequent AJAX requests. Once an attacker possesses a valid nonce, they can craft POST requests containing malicious PHP code in the custom logic field, which is then executed directly by the server without further validation or sanitization.
The operational impact of this vulnerability is severe, as it grants Remote Code Execution capabilities to any authenticated user on the WordPress site. Even users with low-level privileges such as Subscribers can escalate their access and execute arbitrary commands on the web server. This could lead to data exfiltration, installation of backdoors, defacement of the website, or use of the compromised server for further attacks against other systems within the network. The ability to run PHP code means attackers have full control over the application context, including database interactions, file system operations, and integration with other plugins or themes that may expose additional attack surfaces.
This vulnerability aligns with CWE-269 Improper Privilege Assignment, as the software fails to enforce proper access controls for privileged functionality. Additionally, it relates to CWE-78 OS Command Injection due to the use of eval() which allows execution of arbitrary code based on user input. From an ATT&CK perspective, this exploitation technique falls under T1059 Command and Scripting Interpreter, specifically PHP scripting, as attackers leverage native system interpreters to execute malicious payloads. The exposure of authentication tokens via publicly accessible scripts also reflects weaknesses in secure configuration practices often associated with CWE-284 Improper Access Control.
To mitigate this vulnerability, administrators should immediately update the Welcomizer plugin to a patched version where these authorization checks have been implemented and unsafe eval usage has been removed or replaced with safer alternatives such as dedicated API endpoints for custom logic execution that do not involve direct code evaluation. If updating is not immediately possible, temporary mitigations include restricting access to the twiz-ajax.js.php file via web server configuration rules to prevent nonce leakage from unauthenticated users. Additionally, implementing strict input validation and output encoding on all user-supplied data before processing can reduce the risk of successful exploitation. Regular security audits and penetration testing should be conducted to identify similar patterns in other plugins or custom code that may exhibit analogous weaknesses in authorization logic and unsafe function usage.