CVE-2025-30342
📋 TL;DR
This stored cross-site scripting (XSS) vulnerability in OpenSlides allows attackers to inject malicious JavaScript into meeting descriptions, notes, and agenda topics. When users hover over specially crafted links, the JavaScript executes in their session context. All OpenSlides users who can view meeting content are potentially affected.
💻 Affected Systems
- OpenSlides
📦 What is this software?
Openslides by Openslides
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, perform actions as authenticated users, redirect to malicious sites, or compromise user accounts through social engineering.
Likely Case
Attackers inject malicious links that execute JavaScript when users hover over them, potentially stealing session data or performing unauthorized actions.
If Mitigated
With proper input validation and output encoding, the risk is limited to authenticated users viewing malicious content.
🎯 Exploit Status
Exploitation requires ability to create or edit meeting content. The vulnerability is publicly documented with technical details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.2.5
Vendor Advisory: https://github.com/OpenSlides/OpenSlides/releases/tag/4.2.5
Restart Required: Yes
Instructions:
1. Backup your OpenSlides installation and database. 2. Update to OpenSlides 4.2.5 or later. 3. Restart the OpenSlides service. 4. Verify the update was successful.
🔧 Temporary Workarounds
Disable rich text editor
allConfigure OpenSlides to use plain text only for meeting descriptions and notes
Content Security Policy
allImplement strict CSP headers to prevent inline JavaScript execution
🧯 If You Can't Patch
- Restrict user permissions for creating/editing meeting content to trusted users only
- Implement web application firewall rules to block malicious HTML attributes in user input
🔍 How to Verify
Check if Vulnerable:
Check if OpenSlides version is below 4.2.5 in the web interface or configuration filesCheck Version:
Check the OpenSlides web interface or review the package version in your deploymentVerify Fix Applied:
Verify the version is 4.2.5 or higher and test that HTML attributes cannot be injected into links📡 Detection & Monitoring
Log Indicators:
- Unusual HTML content in meeting descriptions
- Multiple rapid edits to meeting content
- User complaints about unexpected popups or redirects
Network Indicators:
- Outbound connections to suspicious domains after viewing meeting content
- Unusual JavaScript execution patterns
SIEM Query:
Search for HTML content containing 'onmouseover', 'onclick', or other event handlers in meeting description fields