CVE-2020-1514
📋 TL;DR
This is an authenticated cross-site scripting (XSS) vulnerability in Microsoft SharePoint Server that allows attackers to inject malicious scripts into web pages. When exploited, these scripts execute with the victim's permissions, potentially enabling unauthorized data access, content manipulation, and account takeover. Only authenticated users can exploit this vulnerability against affected SharePoint servers.
💻 Affected Systems
- Microsoft SharePoint Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker could steal sensitive data, modify or delete SharePoint content, escalate privileges, and maintain persistent access through backdoors.
Likely Case
Attackers with valid credentials could perform session hijacking, data exfiltration, and limited content manipulation within the SharePoint environment.
If Mitigated
With proper input validation and output encoding, the risk is reduced to minimal, though authenticated users could still attempt exploitation.
🎯 Exploit Status
Exploitation requires authenticated access to SharePoint; attacker must craft malicious web requests
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security update available through Microsoft Update; specific version depends on SharePoint edition
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1514
Restart Required: Yes
Instructions:
1. Apply Microsoft security update through Windows Update
2. Alternatively, download and install the standalone security update from Microsoft Update Catalog
3. Restart SharePoint services or the server as required
🔧 Temporary Workarounds
Input Validation Enhancement
windowsImplement additional input validation and output encoding for SharePoint web requests
Content Security Policy
allImplement strict Content Security Policy headers to limit script execution
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to detect and block XSS payloads
- Restrict authenticated user permissions to minimum required levels
🔍 How to Verify
Check if Vulnerable:
Check SharePoint version and compare against 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 with script-like content to SharePoint endpoints
- Multiple failed authentication attempts followed by successful login and suspicious requests
Network Indicators:
- HTTP requests containing script tags or JavaScript payloads to SharePoint URLs
- Unusual outbound connections from SharePoint server after user interaction
SIEM Query:
source="sharepoint" AND (http_method="POST" AND (uri="*aspx*" OR uri="*ashx*") AND (content="*<script>*" OR content="*javascript:*"))