CVE-2024-50428: Multi Step Form Auth Bypass Vulnerability

CVE-2024-50428 Overview

CVE-2024-50428 is a missing authorization vulnerability in the Mondula Multi Step Form plugin for WordPress. The flaw affects all versions up to and including 1.7.21. The plugin fails to enforce access control checks on sensitive functionality, allowing unauthenticated network attackers to invoke plugin operations that should require authorization. The issue is tracked under CWE-862: Missing Authorization and is reachable over the network without user interaction.

Critical Impact

Unauthenticated attackers can exploit broken access control to bypass authorization on WordPress sites running vulnerable Multi Step Form plugin versions, impacting confidentiality, integrity, and availability.

Affected Products

• Mondula Multi Step Form WordPress plugin versions through 1.7.21
• WordPress sites with the multi-step-form plugin installed and activated
• Any deployment exposing the plugin's endpoints to untrusted networks

Discovery Timeline

• 2024-10-29 - CVE-2024-50428 published to the National Vulnerability Database
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2024-50428

Vulnerability Analysis

The Mondula Multi Step Form plugin exposes functionality without verifying that the calling user has the required permissions. This is a classic broken access control defect where the plugin relies on the presence of an action or endpoint rather than validating the requestor's capability or nonce. An attacker reaching the plugin's HTTP endpoints can invoke privileged operations directly.

The defect maps to CWE-862: Missing Authorization. Because the plugin operates inside WordPress, abused endpoints inherit the site's execution context and can affect form data, plugin configuration, or related stored content. The Patchstack advisory tracks this as a broken access control issue affecting the plugin up through version 1.7.21. See the Patchstack WordPress Vulnerability advisory for vendor tracking details.

Root Cause

The root cause is the absence of capability checks (current_user_can()) and nonce validation (check_ajax_referer() or wp_verify_nonce()) on plugin handlers. Without these guards, WordPress executes the requested action regardless of the requestor's identity or role.

Attack Vector

The vulnerability is exploitable over the network with no authentication and no user interaction. An attacker crafts an HTTP request targeting the plugin's vulnerable handler on a public WordPress site. Because the plugin does not validate authorization, the request is processed and the unauthorized action is performed. No code example is published by the vendor or in a verified proof-of-concept repository, so exploitation details are not reproduced here.

Detection Methods for CVE-2024-50428

Indicators of Compromise

• Unexpected POST or GET requests to admin-ajax.php referencing Multi Step Form actions from unauthenticated sessions
• Modifications to Multi Step Form configuration, submissions, or related options performed outside of administrator sessions
• Anomalous spikes in traffic to /wp-content/plugins/multi-step-form/ resources

Detection Strategies

• Inventory WordPress installations and identify hosts running the multi-step-form plugin at version 1.7.21 or earlier
• Review web server access logs for requests to plugin endpoints lacking a valid authenticated session cookie or nonce parameter
• Correlate WordPress audit logs with web traffic to identify configuration or content changes that did not originate from a logged-in administrator

Monitoring Recommendations

• Enable WordPress activity logging to capture plugin setting changes and form submission events
• Forward web server and WordPress logs to a centralized SIEM for correlation against unauthenticated administrative actions
• Alert on admin-ajax.php traffic patterns that target plugin actions from external IP ranges at high rates

How to Mitigate CVE-2024-50428

Immediate Actions Required

• Identify all WordPress sites running Mondula Multi Step Form and confirm the installed version
• Update the plugin to a version released after 1.7.21 that addresses the broken access control issue
• If an updated version is not available for your environment, deactivate and remove the plugin until a fix can be applied

Patch Information

Mondula has released plugin updates addressing this issue. Refer to the Patchstack WordPress Vulnerability advisory for the fixed version and upgrade guidance. Apply the update through the WordPress admin plugin manager or via wp-cli.

Workarounds

• Deactivate the Multi Step Form plugin on affected sites until patched
• Restrict access to wp-admin/admin-ajax.php and plugin paths using a Web Application Firewall (WAF) rule that blocks unauthenticated invocations of plugin actions
• Limit administrative access to WordPress to trusted IP ranges where feasible

# Update the plugin using wp-cli
wp plugin update multi-step-form

# Or deactivate the plugin if an update is not yet available
wp plugin deactivate multi-step-form