CVE-2025-49745
📋 TL;DR
This cross-site scripting (XSS) vulnerability in Microsoft Dynamics 365 (on-premises) allows attackers to inject malicious scripts into web pages. When exploited, it enables spoofing attacks where users can be tricked into interacting with fake content. Organizations running affected on-premises Dynamics 365 deployments are at risk.
💻 Affected Systems
- Microsoft Dynamics 365 (on-premises)
📦 What is this software?
Dynamics 365 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, credentials, or sensitive data, perform actions as authenticated users, or redirect users to malicious sites.
Likely Case
Attackers create convincing spoofed pages to trick users into revealing credentials or sensitive information through social engineering.
If Mitigated
With proper input validation and output encoding, the attack surface is significantly reduced, though the vulnerability still exists.
🎯 Exploit Status
Requires attacker to craft malicious input that gets reflected in web pages; typical XSS exploitation techniques apply.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft's security update for specific version
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-49745
Restart Required: No
Instructions:
1. Review Microsoft's security advisory for CVE-2025-49745. 2. Apply the security update provided by Microsoft. 3. Test the update in a non-production environment first. 4. Deploy to production systems during maintenance windows.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement strict input validation and output encoding for all user-supplied data in Dynamics 365 customizations
Content Security Policy (CSP)
allImplement a strict Content Security Policy to mitigate XSS impact
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block XSS payloads
- Restrict access to Dynamics 365 to trusted networks only
🔍 How to Verify
Check if Vulnerable:
Check Dynamics 365 version against Microsoft's security advisory; test for XSS vulnerabilities using security scanning toolsCheck Version:
Check Dynamics 365 version through administration console or PowerShell: Get-Command *dynamics*Verify Fix Applied:
Verify the security update is installed; test with XSS payloads to confirm they are properly sanitized📡 Detection & Monitoring
Log Indicators:
- Unusual long parameter values in web requests
- Script tags or JavaScript in URL parameters
- Multiple failed XSS attempts
Network Indicators:
- HTTP requests containing common XSS payload patterns
- Unusual outbound connections following XSS exploitation
SIEM Query:
source="dynamics365" AND (url="*<script>*" OR param="*javascript:*" OR param="*onclick=*" OR param="*alert(*")