CVE-2023-34089
📋 TL;DR
CVE-2023-34089 is a cross-site scripting (XSS) vulnerability in Decidim's processes filter feature that allows remote attackers to execute JavaScript in the context of logged-in users. This could enable attackers to make users endorse or support proposals without their consent. All Decidim instances with vulnerable versions are affected.
💻 Affected Systems
- Decidim
📦 What is this software?
Decidim by Decidim
Decidim by Decidim
⚠️ Risk & Real-World Impact
Worst Case
Attackers could perform actions as authenticated users, including unauthorized endorsements, data theft via session hijacking, or account takeover.
Likely Case
Attackers trick users into endorsing proposals they didn't intend to support, potentially manipulating participatory democracy outcomes.
If Mitigated
With proper input validation and output encoding, the XSS payloads would be neutralized before execution.
🎯 Exploit Status
XSS vulnerabilities are commonly exploited; the advisory provides enough detail for attackers to craft payloads.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.26.7 or 0.27.3
Vendor Advisory: https://github.com/decidim/decidim/security/advisories/GHSA-5652-92r9-3fx9
Restart Required: Yes
Instructions:
1. Backup your Decidim instance and database. 2. Update Gemfile to require 'decidim' version '~> 0.26.7' or '~> 0.27.3'. 3. Run 'bundle update decidim'. 4. Restart the Rails application server.
🔧 Temporary Workarounds
Input Sanitization Enhancement
allImplement additional input validation and output encoding for the processes filter parameters
# Add custom sanitization in relevant controller/helper files
# Example: sanitize(params[:filter]) before processing
🧯 If You Can't Patch
- Implement a web application firewall (WAF) with XSS protection rules to block malicious payloads.
- Disable or restrict the processes filter feature if not essential for your deployment.
🔍 How to Verify
Check if Vulnerable:
Check your Gemfile.lock or run 'bundle show decidim' to see the installed version. If version is below 0.26.7 (for 0.26.x) or below 0.27.3 (for 0.27.x), you are vulnerable.Check Version:
bundle show decidim | grep -o 'decidim ([0-9.]*)'Verify Fix Applied:
After updating, verify the version with 'bundle show decidim' shows 0.26.7 or higher, or 0.27.3 or higher. Test the processes filter feature with safe test payloads.📡 Detection & Monitoring
Log Indicators:
- Unusual JavaScript payloads in filter parameters in Rails logs
- Multiple endorsement/support actions from single user sessions
Network Indicators:
- HTTP requests with JavaScript in filter query parameters
- Unexpected redirects or script tags in responses
SIEM Query:
source="rails.log" AND ("filter" AND ("script" OR "javascript" OR "onerror" OR "onload"))🔗 References
- https://github.com/decidim/decidim/releases/tag/v0.26.6
- https://github.com/decidim/decidim/releases/tag/v0.27.3
- https://github.com/decidim/decidim/security/advisories/GHSA-5652-92r9-3fx9
- https://github.com/decidim/decidim/releases/tag/v0.26.6
- https://github.com/decidim/decidim/releases/tag/v0.27.3
- https://github.com/decidim/decidim/security/advisories/GHSA-5652-92r9-3fx9
