CVE-2023-25154
📋 TL;DR
This vulnerability allows attackers to execute arbitrary JavaScript code in victims' browsers by exploiting improper URL validation in Misskey's ActivityPub implementation. It affects all Misskey instances running versions before 13.5.0. Attackers can craft malicious links that execute when users view content from untrusted remote instances.
💻 Affected Systems
- Misskey
📦 What is this software?
Misskey by Misskey
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover, data theft, session hijacking, and further server compromise through client-side attacks.
Likely Case
Session hijacking, account compromise, data exfiltration, and malicious actions performed as the victim user.
If Mitigated
Limited impact with proper content security policies and user awareness, but still potentially dangerous.
🎯 Exploit Status
Exploitation requires victims to view malicious content from attacker-controlled instances.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 13.5.0
Vendor Advisory: https://github.com/misskey-dev/misskey/security/advisories/GHSA-pfp5-r48x-fg25
Restart Required: Yes
Instructions:
1. Backup your instance data. 2. Update Misskey to version 13.5.0 or later using your package manager or git pull. 3. Run 'pnpm install' to update dependencies. 4. Restart the Misskey service.
🔧 Temporary Workarounds
Disable Remote Viewing
allPrevent users from viewing content on remote instances where the vulnerability could be triggered.
Content Security Policy
linuxImplement strict CSP headers to block inline JavaScript and restrict script sources.
add_header Content-Security-Policy "default-src 'self'; script-src 'self'" always;
🧯 If You Can't Patch
- Disable ActivityPub federation entirely if not required
- Educate users to never use 'view on remote' feature for untrusted instances
🔍 How to Verify
Check if Vulnerable:
Check if Misskey version is below 13.5.0 in admin panel or via package manager.Check Version:
cat package.json | grep versionVerify Fix Applied:
Confirm version is 13.5.0 or higher and test that javascript: URLs are properly sanitized in remote content.📡 Detection & Monitoring
Log Indicators:
- Unusual JavaScript execution in user sessions
- Multiple failed URL validation attempts
Network Indicators:
- Suspicious javascript: scheme URLs in ActivityPub payloads
SIEM Query:
source="misskey.log" AND "javascript:" AND "remote"