CVE-2023-53978
📋 TL;DR
CVE-2023-53978 is a stored cross-site scripting vulnerability in myBB Forums that allows authenticated administrators to inject malicious JavaScript when creating forum announcements. This vulnerability affects myBB Forums version 1.8.26 and allows attackers to execute arbitrary scripts in users' browsers when they view announcements.
💻 Affected Systems
- myBB Forums
📦 What is this software?
Mybb by Mybb
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, redirect users to malicious sites, perform actions on behalf of users, or install malware through the forum interface.
Likely Case
Session hijacking, credential theft, or defacement of forum pages through malicious script execution.
If Mitigated
Limited impact if proper input validation and output encoding are implemented, or if administrator accounts are secured.
🎯 Exploit Status
Exploitation requires administrator credentials. Public exploit code is available on Exploit-DB.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.8.27 or later
Vendor Advisory: https://mybb.com/
Restart Required: No
Instructions:
1. Backup your myBB installation and database. 2. Download the latest myBB version from mybb.com. 3. Replace all files except inc/config.php and inc/settings.php. 4. Run the upgrade script if required. 5. Verify the announcement functionality works correctly.
🔧 Temporary Workarounds
Input Validation Filter
allAdd custom input validation to sanitize announcement title fields
Edit inc/plugins/announcements.php to add HTML entity encoding for title inputs
Disable Announcements
allTemporarily disable the forum announcement feature
Edit inc/config.php to set $config['enable_announcements'] = false;
🧯 If You Can't Patch
- Restrict administrator account access to trusted personnel only
- Implement web application firewall rules to block XSS payloads in announcement titles
🔍 How to Verify
Check if Vulnerable:
Check if running myBB version 1.8.26. Attempt to create an announcement with a test XSS payload like <script>alert('test')</script> in the title field.Check Version:
Check inc/version.php or admin dashboard for version informationVerify Fix Applied:
After patching, test that XSS payloads in announcement titles are properly sanitized and do not execute.📡 Detection & Monitoring
Log Indicators:
- Unusual administrator activity creating announcements
- Announcement titles containing script tags or JavaScript code
Network Indicators:
- HTTP requests with script payloads in announcement parameters
- Unexpected JavaScript execution from forum pages
SIEM Query:
source="mybb_logs" AND (message="*announcement*" AND message="*script*" OR message="*<script>*")