CVE-2025-23850: Mojo Under Construction XSS Vulnerability

CVE-2025-23850 Overview

CVE-2025-23850 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the Mojo Under Construction WordPress plugin developed by mojowill. This vulnerability allows attackers to inject malicious scripts into web pages viewed by other users through improper neutralization of user-supplied input during web page generation.

The vulnerability exists in versions up to and including 1.1.2 of the plugin, which is commonly used to display "under construction" or maintenance pages on WordPress sites. When exploited, an attacker can craft malicious URLs that, when clicked by authenticated users or administrators, execute arbitrary JavaScript in the context of the victim's browser session.

Critical Impact

Attackers can leverage this Reflected XSS vulnerability to steal session cookies, perform unauthorized actions on behalf of authenticated users, redirect victims to malicious websites, or deface web pages. WordPress administrators are particularly at risk as exploitation could lead to full site compromise.

Affected Products

• Mojo Under Construction WordPress plugin versions through 1.1.2
• WordPress installations using the mojo-under-construction plugin
• Sites running vulnerable versions without proper input validation

Discovery Timeline

• 2025-03-03 - CVE CVE-2025-23850 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-23850

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), which represents one of the most common web application security flaws. The Mojo Under Construction plugin fails to properly sanitize user-controlled input before reflecting it back in the HTML response, allowing attackers to inject malicious JavaScript code.

Reflected XSS attacks require social engineering to trick victims into clicking malicious links. In the context of a WordPress maintenance plugin, this is particularly concerning because site administrators are the primary users who would interact with the plugin's interface, making them high-value targets for attackers seeking elevated privileges.

The network-based attack vector means exploitation can occur remotely without requiring prior authentication to the vulnerable system. However, successful exploitation does require user interaction—specifically, the victim must click a crafted malicious link.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding within the Mojo Under Construction plugin. When user-supplied data is processed by the plugin, it fails to properly sanitize or escape special characters that have meaning in HTML and JavaScript contexts. This allows attackers to break out of the intended data context and inject executable script code.

WordPress plugins that handle user input should utilize WordPress's built-in sanitization functions such as esc_html(), esc_attr(), and wp_kses() to prevent XSS attacks. The absence or improper implementation of these security controls in the affected plugin versions creates the vulnerability condition.

Attack Vector

The attack leverages the network-accessible nature of web applications to deliver malicious payloads. An attacker constructs a specially crafted URL containing JavaScript code within vulnerable parameters. When an unsuspecting user clicks this link, the malicious script executes in their browser within the security context of the WordPress site.

The exploitation flow typically involves:

1. Attacker identifies vulnerable parameter(s) in the Mojo Under Construction plugin
2. Attacker crafts a malicious URL with injected JavaScript payload
3. Attacker distributes the malicious link via phishing emails, social media, or compromised websites
4. Victim clicks the link while authenticated to the WordPress site
5. Malicious JavaScript executes with the victim's session privileges

For detailed technical analysis of this vulnerability, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-23850

Indicators of Compromise

• Unusual URL parameters containing JavaScript code or HTML entities in requests to WordPress plugin endpoints
• Access logs showing requests with encoded <script> tags or event handlers like onerror, onload, or onclick
• User reports of unexpected redirects or pop-ups when accessing WordPress admin pages
• Browser security warnings or Content Security Policy (CSP) violations in client-side logs

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block requests containing XSS payloads targeting WordPress plugin parameters
• Implement Content Security Policy headers to mitigate the impact of successful XSS exploitation by restricting script execution sources
• Monitor server access logs for suspicious query strings containing encoded special characters such as %3C, %3E, %22, or %27
• Utilize WordPress security plugins that scan for known vulnerable plugin versions and alert administrators

Monitoring Recommendations

• Enable detailed logging for all WordPress plugin interactions, particularly those involving user-supplied input
• Configure alerting for unusual patterns of access to the Mojo Under Construction plugin endpoints
• Implement real-time monitoring for CSP violation reports which may indicate attempted XSS exploitation
• Regularly audit installed plugin versions against known vulnerability databases

How to Mitigate CVE-2025-23850

Immediate Actions Required

• Audit your WordPress installation to determine if the Mojo Under Construction plugin is installed and identify the current version
• If using version 1.1.2 or earlier, consider temporarily disabling or removing the plugin until a patched version is available
• Implement a Web Application Firewall (WAF) with XSS protection rules as a compensating control
• Review server logs for any signs of attempted exploitation

Patch Information

At the time of this advisory, site administrators should check the official WordPress plugin repository for updates to the Mojo Under Construction plugin. Monitor the plugin author's communications and the Patchstack vulnerability database for patch availability announcements.

If no patch is available, evaluate alternative maintenance mode plugins that have better security track records or consider implementing maintenance mode functionality at the web server level instead.

Workarounds

• Disable the Mojo Under Construction plugin if it is not actively needed for site operations
• Implement strict Content Security Policy (CSP) headers to limit the impact of XSS attacks by controlling which scripts can execute
• Use a WAF to filter requests containing common XSS payloads before they reach the WordPress application
• Restrict access to the WordPress admin panel to trusted IP addresses to reduce the attack surface

# Example Content Security Policy header configuration for Apache
# Add to .htaccess or virtual host configuration
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"

# Example for Nginx - add to server block
# add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';";