CVE-2023-36886
📋 TL;DR
This is a cross-site scripting (XSS) vulnerability in Microsoft Dynamics 365 on-premises that allows attackers to inject malicious scripts into web pages viewed by other users. Attackers could steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. Organizations running vulnerable on-premises Dynamics 365 installations are affected.
💻 Affected Systems
- Microsoft Dynamics 365 (on-premises)
📦 What is this software?
Dynamics 365 by Microsoft
Dynamics 365 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal administrator credentials, hijack user sessions, perform unauthorized actions in Dynamics 365, and potentially pivot to other systems using stolen credentials.
Likely Case
Attackers steal user session cookies or credentials, leading to unauthorized access to Dynamics 365 data and functionality.
If Mitigated
Limited impact with proper input validation, output encoding, and Content Security Policy headers in place.
🎯 Exploit Status
XSS vulnerabilities typically have low exploitation complexity once the vulnerable endpoint is identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply the security update from Microsoft's July 2023 Patch Tuesday
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-36886
Restart Required: Yes
Instructions:
1. Download the security update from Microsoft Update Catalog. 2. Apply the update to all affected Dynamics 365 on-premises servers. 3. Restart the servers as required. 4. Test functionality after patching.
🔧 Temporary Workarounds
Implement Content Security Policy
allAdd Content Security Policy headers to restrict script execution sources
Add 'Content-Security-Policy' header to web server configuration
Input Validation Enhancement
allImplement additional input validation for user-supplied data
Configure web application firewall rules to block suspicious script patterns
🧯 If You Can't Patch
- Implement web application firewall with XSS protection rules
- Restrict access to Dynamics 365 to trusted networks only
- Implement strict Content Security Policy headers
- Monitor for suspicious script injection attempts in logs
🔍 How to Verify
Check if Vulnerable:
Check if your Dynamics 365 on-premises installation has the July 2023 security updates appliedCheck Version:
Check Dynamics 365 version through administrative interface or PowerShell: Get-Command -Module Microsoft.Dynamics*Verify Fix Applied:
Verify the security update is installed and test for XSS vulnerabilities using security testing tools📡 Detection & Monitoring
Log Indicators:
- Unusual script tags in HTTP requests
- Suspicious JavaScript payloads in URLs or form data
- Multiple failed XSS attempts
Network Indicators:
- HTTP requests containing script injection patterns
- Unusual outbound connections following XSS exploitation
SIEM Query:
source="web_server_logs" AND ("<script>" OR "javascript:" OR "onload=" OR "onerror=") AND status=200