CVE-2020-1500
📋 TL;DR
This is a cross-site scripting (XSS) vulnerability in Microsoft SharePoint Server where authenticated attackers can send specially crafted requests to bypass input sanitization. Successful exploitation allows attackers to execute scripts in the victim's security context, potentially reading unauthorized content, modifying permissions, deleting data, or injecting malicious content. Only authenticated users with SharePoint access are affected.
💻 Affected Systems
- Microsoft SharePoint Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attacker gains full control of SharePoint site through victim's credentials, modifies all permissions, deletes critical data, and injects persistent malware affecting all users.
Likely Case
Attacker steals sensitive documents, modifies permissions for privilege escalation, or injects malicious scripts to capture user credentials.
If Mitigated
Limited impact due to proper input validation, network segmentation, and least privilege access controls preventing script execution.
🎯 Exploit Status
Requires authenticated access and knowledge of SharePoint request structure; no public exploit code known
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security update through Microsoft Update or specific SharePoint cumulative update
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1500
Restart Required: Yes
Instructions:
1. Apply Microsoft security update through Windows Update or download from Microsoft Update Catalog. 2. Restart SharePoint servers. 3. Test SharePoint functionality after patching.
🔧 Temporary Workarounds
Input Validation Enhancement
windowsImplement additional input validation and output encoding for SharePoint web requests
🧯 If You Can't Patch
- Implement strict network segmentation to isolate SharePoint servers from untrusted networks
- Enforce least privilege access controls and monitor for unusual authenticated user activity
🔍 How to Verify
Check if Vulnerable:
Check SharePoint Server version and compare with patched versions in Microsoft advisoryCheck Version:
Get-SPFarm | Select BuildVersionVerify Fix Applied:
Verify security update is installed via Windows Update history or SharePoint version check📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to SharePoint endpoints
- Multiple failed authentication attempts followed by successful login with script-like payloads
Network Indicators:
- HTTP requests containing script tags or encoded payloads to SharePoint URLs
- Unusual outbound connections from SharePoint servers
SIEM Query:
source="sharepoint" AND (http_method="POST" AND (uri="*_layouts/*" OR uri="*_vti_bin/*") AND (content="<script>" OR content="javascript:"))