CVE-2023-28309
📋 TL;DR
This vulnerability allows attackers to inject malicious scripts into Microsoft Dynamics 365 (on-premises) web pages, which are then executed in victims' browsers when they view those pages. It affects organizations running vulnerable versions of Microsoft Dynamics 365 on-premises deployments. Attackers could steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users.
💻 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
Complete account takeover, data theft, and lateral movement within the organization by stealing administrator credentials and session tokens.
Likely Case
Session hijacking, credential theft, and defacement of Dynamics 365 interfaces for phishing or malware distribution.
If Mitigated
Limited impact due to proper input validation, output encoding, and Content Security Policy headers preventing script execution.
🎯 Exploit Status
Requires attacker to trick authenticated user into visiting malicious link or page. Typically requires some user interaction.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply the security update from Microsoft's May 2023 Patch Tuesday or later
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-28309
Restart Required: Yes
Instructions:
1. Download the security update from Microsoft Update Catalog
2. Apply the update to all affected Dynamics 365 servers
3. Restart the Dynamics 365 services
4. Test functionality after patching
🔧 Temporary Workarounds
Implement Content Security Policy
allAdd CSP headers to restrict script execution to trusted sources only
Add 'Content-Security-Policy' header with appropriate directives in web.config or server configuration
Input Validation Enhancement
allImplement additional input validation for user-supplied data in Dynamics 365 customizations
Review and enhance input validation in custom code and configurations
🧯 If You Can't Patch
- Implement web application firewall (WAF) with XSS protection rules
- Disable unnecessary Dynamics 365 web interfaces and reduce attack surface
🔍 How to Verify
Check if Vulnerable:
Check Dynamics 365 version against Microsoft's security bulletin and verify if May 2023 patches are appliedCheck Version:
Check Dynamics 365 version in Administration settings or review installed updates in Control PanelVerify Fix Applied:
Verify patch installation through Windows Update history and test XSS payloads are properly sanitized📡 Detection & Monitoring
Log Indicators:
- Unusual script tags or JavaScript in URL parameters in web server logs
- Multiple failed login attempts followed by successful logins from different locations
Network Indicators:
- Suspicious JavaScript payloads in HTTP requests to Dynamics 365 endpoints
- Unexpected redirects to external domains
SIEM Query:
source="web_server_logs" AND (url="*<script*" OR url="*javascript:*" OR url="*onload=*" OR url="*onerror=*")