CVE-2025-66481
📋 TL;DR
DeepChat versions 0.5.1 and below are vulnerable to cross-site scripting (XSS) attacks through improperly sanitized Mermaid diagram content. Attackers can bypass existing filters using unquoted HTML attributes and HTML entity encoding to execute arbitrary JavaScript code on victims' machines, potentially leading to remote code execution via the electron.ipcRenderer interface. This affects all users running vulnerable DeepChat instances.
💻 Affected Systems
- DeepChat
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution on victim's machine through electron.ipcRenderer, allowing complete system compromise, data theft, and lateral movement within the network.
Likely Case
Cross-site scripting leading to session hijacking, credential theft, and unauthorized access to chat data and AI model interactions.
If Mitigated
Limited impact if proper content security policies and input validation are in place, though XSS could still lead to session compromise.
🎯 Exploit Status
Exploitation requires crafting malicious Mermaid content but does not require authentication. The bypass technique using unquoted attributes and HTML entity encoding is documented in the advisory.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None
Vendor Advisory: https://github.com/ThinkInAIXYZ/deepchat/security/advisories/GHSA-h9f5-7hhf-fqm4
Restart Required: Yes
Instructions:
No official patch available. Monitor the GitHub repository for updates and apply immediately when released.
🔧 Temporary Workarounds
Disable Mermaid functionality
allTemporarily disable Mermaid diagram rendering in DeepChat configuration
Edit DeepChat configuration to remove or disable Mermaid-related components
Implement strict CSP headers
allAdd Content Security Policy headers to restrict script execution
Add 'Content-Security-Policy: script-src 'self'' to web server headers
🧯 If You Can't Patch
- Isolate DeepChat instances in network segments with strict egress filtering
- Implement web application firewall (WAF) rules to block suspicious Mermaid content patterns
🔍 How to Verify
Check if Vulnerable:
Check DeepChat version in package.json or application settings. If version is 0.5.1 or below, the system is vulnerable.Check Version:
Check package.json for version field or run 'npm list deepchat' in installation directoryVerify Fix Applied:
When patch becomes available, verify version is above 0.5.1 and test Mermaid content sanitization.📡 Detection & Monitoring
Log Indicators:
- Unusual Mermaid content patterns in request logs
- JavaScript execution errors in electron renderer logs
- Suspicious ipcRenderer calls
Network Indicators:
- HTTP requests containing encoded HTML attributes in Mermaid content
- Outbound connections from DeepChat to unexpected destinations
SIEM Query:
source="deepchat" AND (mermaid OR "<script>" OR "javascript:")