CVE-2025-26756: MTG Card Tooltips Stored XSS Vulnerability

CVE-2025-26756 Overview

A Stored Cross-Site Scripting (XSS) vulnerability has been identified in the Magic the Gathering Card Tooltips WordPress plugin developed by grimdonkey. This vulnerability allows attackers to inject malicious scripts that persist in the application and execute when other users access the affected pages. The flaw stems from improper neutralization of user input during web page generation.

Critical Impact

Attackers can inject persistent malicious JavaScript code that executes in the browsers of all users who view the affected content, potentially leading to session hijacking, credential theft, or malicious redirects.

Affected Products

• Magic the Gathering Card Tooltips plugin version 3.5.0 and earlier
• WordPress installations using the magic-the-gathering-card-tooltips plugin
• All websites with the vulnerable plugin versions deployed

Discovery Timeline

• 2025-02-22 - CVE-2025-26756 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2025-26756

Vulnerability Analysis

This Stored XSS vulnerability (CWE-79) occurs when the Magic the Gathering Card Tooltips plugin fails to properly sanitize user-supplied input before incorporating it into dynamically generated web pages. Unlike reflected XSS attacks that require victims to click malicious links, stored XSS payloads persist in the application's database and automatically execute when legitimate users view the compromised content.

The vulnerability is particularly concerning in a WordPress context because plugin functionality often processes user input for displaying card tooltips. When this input lacks proper sanitization, malicious JavaScript can be stored and served to all visitors, including administrators with elevated privileges.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and output encoding within the plugin's codebase. Specifically, the plugin does not adequately sanitize or escape user-controlled data before storing it in the database or rendering it in HTML output. WordPress provides built-in functions like esc_html(), esc_attr(), and wp_kses() for proper output escaping, but the vulnerable code paths in this plugin fail to implement these security controls correctly.

Attack Vector

An attacker can exploit this vulnerability by submitting malicious JavaScript code through input fields processed by the plugin. The malicious payload is then stored in the WordPress database and executed in the browsers of users who subsequently view the affected content. This attack can be leveraged to:

• Steal session cookies and authentication tokens
• Perform actions on behalf of authenticated users
• Redirect users to phishing or malware distribution sites
• Deface website content
• Capture sensitive information entered on the page

The vulnerability affects plugin functionality that handles card tooltip data, where insufficient input sanitization allows script injection through specially crafted card names or tooltip content.

Detection Methods for CVE-2025-26756

Indicators of Compromise

• Unusual JavaScript code fragments in database entries related to Magic the Gathering card tooltips
• Unexpected <script> tags, event handlers (e.g., onerror, onload), or encoded JavaScript in plugin-related content
• Reports from users experiencing unexpected redirects or browser behavior when viewing card tooltips
• Web application firewall (WAF) logs showing blocked XSS payloads targeting the plugin

Detection Strategies

• Review WordPress database tables associated with the Magic the Gathering Card Tooltips plugin for suspicious content containing script tags or encoded JavaScript
• Implement content security policy (CSP) headers and monitor for violations that may indicate XSS attempts
• Deploy web application firewall rules to detect and block common XSS payload patterns targeting WordPress plugins
• Conduct regular security scans using WordPress security plugins or external vulnerability scanners

Monitoring Recommendations

• Enable detailed logging for WordPress database modifications and plugin activity
• Monitor browser console errors reported through client-side telemetry for unexpected script execution
• Set up alerts for Content Security Policy violations that may indicate XSS exploitation attempts
• Regularly audit plugin database tables for content containing HTML tags or JavaScript code

How to Mitigate CVE-2025-26756

Immediate Actions Required

• Update the Magic the Gathering Card Tooltips plugin to a patched version when available from the developer
• If no patch is available, consider temporarily deactivating the magic-the-gathering-card-tooltips plugin until a fix is released
• Review and sanitize existing database content associated with the plugin for any malicious payloads
• Implement a Web Application Firewall (WAF) to block common XSS attack patterns

Patch Information

Users should monitor the official WordPress plugin repository and the Patchstack Vulnerability Report for updates regarding a security patch. Version 3.5.0 and all earlier versions are confirmed vulnerable. Website administrators should ensure automatic updates are enabled or manually check for plugin updates regularly.

Workarounds

• Disable the Magic the Gathering Card Tooltips plugin until a patched version is available
• Implement Content Security Policy headers to restrict inline script execution using directives like script-src 'self'
• Deploy a WordPress security plugin with XSS protection capabilities to add an additional layer of defense
• Restrict plugin usage to trusted administrator accounts only and limit contributor access

# Add Content Security Policy header in .htaccess for Apache
# This helps mitigate XSS by restricting script execution sources
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline';"

# Alternative: Add to wp-config.php using PHP
# header("Content-Security-Policy: default-src 'self'; script-src 'self';");