CVE-2026-25016: Nelio Popups Auth Bypass Vulnerability

CVE-2026-25016 Overview

CVE-2026-25016 is a Missing Authorization vulnerability affecting the Nelio Popups WordPress plugin developed by Nelio Software. This broken access control flaw allows attackers to exploit incorrectly configured access control security levels, potentially enabling unauthorized actions within WordPress installations using the vulnerable plugin.

The vulnerability stems from CWE-862 (Missing Authorization), where the plugin fails to properly verify user permissions before allowing certain operations. This type of flaw is particularly concerning in WordPress environments where plugin functionality often extends administrative capabilities.

Critical Impact
Authenticated attackers with low-level privileges can bypass access controls to perform unauthorized modifications to popup configurations and settings within affected WordPress installations.

Affected Products

Nelio Popups WordPress Plugin versions up to and including 1.3.5
WordPress installations with Nelio Popups (nelio-popups) plugin active
All prior versions of the Nelio Popups plugin from initial release through 1.3.5

Discovery Timeline

2026-02-03 - CVE CVE-2026-25016 published to NVD
2026-02-03 - Last updated in NVD database

Technical Details for CVE-2026-25016

Vulnerability Analysis

This vulnerability represents a broken access control condition within the Nelio Popups WordPress plugin. The root issue lies in missing authorization checks that should verify whether a user has appropriate permissions before executing sensitive operations.

In WordPress plugin architecture, proper authorization requires checking user capabilities using functions like current_user_can() before performing privileged actions. When these checks are absent or improperly implemented, users with limited roles (such as subscribers or contributors) may be able to access functionality intended only for administrators.

The network-based attack vector means this vulnerability can be exploited remotely by any authenticated user on the WordPress installation. The exploitation requires only low-level authentication privileges, making it accessible to a wide range of potential attackers who may have basic accounts on vulnerable sites.

Root Cause

The vulnerability originates from CWE-862: Missing Authorization. The Nelio Popups plugin fails to implement proper capability checks on one or more of its AJAX handlers or REST API endpoints. This architectural oversight allows authenticated users to invoke plugin functionality without the plugin verifying that the requesting user has the appropriate WordPress capabilities.

In WordPress development, this commonly occurs when developers use wp_ajax_ hooks without subsequently validating user roles and capabilities within the handler function. The missing authorization check creates a gap where the WordPress authentication system confirms the user is logged in, but the plugin never verifies what that user is permitted to do.

Attack Vector

The attack is network-based and requires an authenticated session with low privileges on the target WordPress installation. An attacker with any authenticated role (including the lowest-level subscriber role) can potentially:

Send crafted requests to vulnerable plugin endpoints
Bypass intended access restrictions on popup management features
Modify popup configurations or settings without proper authorization

The exploitation path involves identifying the unprotected AJAX actions or REST endpoints exposed by the plugin and crafting requests that manipulate popup-related data or settings. Since the vulnerability affects integrity (allowing unauthorized modifications) without impacting confidentiality or availability, the primary risk is unauthorized content manipulation within the popup system.

For detailed technical analysis of this vulnerability, refer to the Patchstack Security Advisory.

Detection Methods for CVE-2026-25016

Indicators of Compromise

Unexpected modifications to Nelio Popups configurations by non-administrator users
WordPress audit logs showing popup-related AJAX requests from low-privileged accounts
Anomalous POST requests to admin-ajax.php with Nelio Popups-related action parameters from subscriber or contributor roles

Detection Strategies

Review WordPress access logs for POST requests to admin-ajax.php containing nelio or popup related action parameters from non-administrative user sessions
Implement Web Application Firewall (WAF) rules to monitor and alert on suspicious plugin endpoint access patterns
Deploy WordPress security plugins that provide real-time capability abuse detection and alerting

Monitoring Recommendations

Enable comprehensive WordPress audit logging to track all user actions, particularly those involving plugin functionality
Configure alerts for any popup configuration changes initiated by non-administrator accounts
Regularly review user activity reports focusing on low-privileged accounts accessing administrative plugin features

How to Mitigate CVE-2026-25016

Immediate Actions Required

Update Nelio Popups plugin to a version newer than 1.3.5 when a patched release becomes available
Audit existing WordPress user accounts and remove unnecessary accounts or reduce privileges where possible
Review recent popup configuration changes for any unauthorized modifications
Consider temporarily deactivating the Nelio Popups plugin on high-value sites until a patch is available

Patch Information

A patched version addressing this missing authorization vulnerability should be obtained from the official WordPress plugin repository or directly from Nelio Software. Monitor the Patchstack Security Advisory for updates on remediation status and patch availability.

Before updating, ensure you have a complete backup of your WordPress installation including the database. After applying any update, verify that popup functionality continues to work as expected.

Workarounds

Restrict WordPress user registration and remove untrusted or unnecessary user accounts to minimize the authenticated attack surface
Implement additional access control at the web server level using .htaccess rules to limit access to admin-ajax.php from specific IP addresses
Deploy a WordPress security plugin that provides additional capability enforcement and can block unauthorized AJAX requests
Consider using a Web Application Firewall configured with WordPress-specific rulesets to detect and block exploitation attempts

bash

# WordPress .htaccess configuration to restrict admin-ajax access
# Add to .htaccess in WordPress root directory

# Limit admin-ajax.php access to logged-in administrators only
<Files admin-ajax.php>
    # Allow legitimate AJAX requests but log suspicious activity
    SetEnvIf Request_Method POST ajax_post_request
    CustomLog ${APACHE_LOG_DIR}/ajax_access.log combined env=ajax_post_request
</Files>