CVE-2018-25249: MyBB My Arcade Plugin XSS Vulnerability

CVE-2018-25249 Overview

CVE-2018-25249 is a persistent cross-site scripting (XSS) vulnerability affecting the MyBB My Arcade Plugin version 1.3. This vulnerability allows authenticated users to inject malicious scripts through arcade game score comments. Attackers can craft HTML and JavaScript payloads in the comment field that execute when other users view or edit the comment, enabling session hijacking, credential theft, and other client-side attacks.

Critical Impact

Authenticated attackers can inject persistent malicious scripts that execute in the context of other users' sessions, potentially leading to account compromise, data theft, and unauthorized actions on behalf of victims.

Affected Products

• MyBB My Arcade Plugin 1.3

Discovery Timeline

• 2026-04-04 - CVE CVE-2018-25249 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2018-25249

Vulnerability Analysis

This persistent cross-site scripting vulnerability (CWE-79) exists in the comment functionality of the MyBB My Arcade Plugin. The plugin fails to properly sanitize user-supplied input in the arcade game score comment field before storing it in the database and rendering it to other users. This stored XSS vulnerability is particularly dangerous because the malicious payload persists in the application and executes automatically whenever a victim views or interacts with the affected comment.

The attack requires a low-privilege authenticated user account to exploit, but the impact extends to any user who views the injected content, including administrators. This could allow privilege escalation through session token theft or enable attackers to perform actions on behalf of higher-privileged users.

Root Cause

The root cause of this vulnerability is improper input validation and output encoding in the My Arcade Plugin's comment handling functionality. The plugin accepts user input in the score comment field without adequately sanitizing HTML special characters or JavaScript code. When this content is later rendered in the browser, the injected script executes within the security context of the viewing user's session.

Attack Vector

The attack is conducted over the network by an authenticated user who submits a specially crafted comment containing malicious HTML or JavaScript code when recording a game score. The payload is stored in the database and subsequently executed in the browsers of other users who view the comment. The attacker can leverage this to steal session cookies, redirect users to phishing pages, modify page content, or perform actions as the victim user.

The vulnerability allows injection through the arcade game score comment field. When a victim views or attempts to edit the malicious comment, the injected JavaScript executes in their browser context. Technical details and exploitation methods are documented in the Exploit-DB #44186 advisory.

Detection Methods for CVE-2018-25249

Indicators of Compromise

• Unusual HTML tags or JavaScript code present in arcade game score comments in the MyBB database
• User reports of unexpected browser behavior or pop-ups when viewing arcade scores
• Web application firewall logs showing blocked XSS patterns in POST requests to arcade-related endpoints
• Unexpected session activity or account behavior indicating potential session hijacking

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block common XSS payload patterns in form submissions
• Enable content security policy (CSP) headers to mitigate script execution from injected content
• Review database entries in arcade score comment tables for suspicious HTML/JavaScript content
• Monitor server access logs for unusual POST requests to the My Arcade plugin endpoints

Monitoring Recommendations

• Enable logging for all user-submitted content to arcade-related functionality
• Configure alerting for CSP violation reports which may indicate XSS exploitation attempts
• Implement regular database scans for stored XSS patterns in user-generated content fields
• Monitor for unusual session activity that could indicate successful XSS-based session theft

How to Mitigate CVE-2018-25249

Immediate Actions Required

• Disable or remove the MyBB My Arcade Plugin version 1.3 until a patched version is available
• Review existing arcade score comments in the database and sanitize any malicious content
• Implement strict Content Security Policy (CSP) headers to prevent inline script execution
• Consider deploying a web application firewall with XSS protection rules

Patch Information

No official patch information is available in the CVE data. Administrators should check the MyBB Mod Details page for any available updates from the plugin developer. Additionally, review the VulnCheck MyBB XSS Advisory for the latest security guidance.

Workarounds

• Disable the arcade comment functionality entirely by modifying plugin settings or code
• Implement server-side input validation to strip HTML tags and encode special characters from comment submissions
• Deploy a reverse proxy or WAF rule to sanitize POST data before it reaches the application
• Restrict arcade score submission to trusted user groups only

# Example: Add Content-Security-Policy header in .htaccess (Apache)
Header always set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'"