CVE-2019-9870
📋 TL;DR
This vulnerability in the w8tcha oEmbed plugin for CKEditor allows cross-site scripting (XSS) attacks through improper handling of SCRIPT elements. Attackers can inject malicious scripts that execute in users' browsers when viewing content containing specially crafted oEmbed elements. Any website using the vulnerable plugin version is affected.
💻 Affected Systems
- w8tcha CKEditor oEmbed Plugin
📦 What is this software?
Oembed by Oembed Project
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of user sessions, credential theft, defacement of websites, and potential server-side code execution if combined with other vulnerabilities.
Likely Case
Session hijacking, credential theft, and unauthorized actions performed on behalf of authenticated users.
If Mitigated
Limited impact with proper content security policies and input validation, potentially reduced to minor data leakage.
🎯 Exploit Status
XSS vulnerabilities are commonly weaponized and require minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version from commit 10f6169e39510bbf5af913886037044458b9dc9b (2019-03-14)
Vendor Advisory: https://github.com/w8tcha/CKEditor-oEmbed-Plugin/commit/10f6169e39510bbf5af913886037044458b9dc9b
Restart Required: No
Instructions:
1. Update the oEmbed plugin to version from commit 10f6169e39510bbf5af913886037044458b9dc9b or later. 2. Replace plugin.js with the patched version. 3. Clear any cached files.
🔧 Temporary Workarounds
Disable oEmbed Plugin
allTemporarily disable the vulnerable oEmbed plugin until patching is possible.
Remove or rename the plugin directory: plugins/oembed
Implement Content Security Policy
allAdd CSP headers to restrict script execution from untrusted sources.
Add header: Content-Security-Policy: script-src 'self'
🧯 If You Can't Patch
- Implement strict input validation and sanitization for all user-provided oEmbed content
- Deploy web application firewall rules to block malicious script injection patterns
🔍 How to Verify
Check if Vulnerable:
Check if plugin.js version predates commit 10f6169e39510bbf5af913886037044458b9dc9b (2019-03-14).Check Version:
Check file modification date or compare with patched version from GitHub repository.Verify Fix Applied:
Verify plugin.js contains the security fixes from commit 10f6169e39510bbf5af913886037044458b9dc9b.📡 Detection & Monitoring
Log Indicators:
- Unusual oEmbed parameter patterns in web server logs
- Multiple requests with script-like payloads in query parameters
Network Indicators:
- Incoming requests containing malicious script tags in oEmbed parameters
SIEM Query:
source="web_server" AND (url CONTAINS "oembed" AND (param CONTAINS "<script" OR param CONTAINS "javascript:"))🔗 References
- https://github.com/w8tcha/CKEditor-oEmbed-Plugin/commit/10f6169e39510bbf5af913886037044458b9dc9b
- https://github.com/w8tcha/CKEditor-oEmbed-Plugin/issues/94
- https://github.com/w8tcha/CKEditor-oEmbed-Plugin/commit/10f6169e39510bbf5af913886037044458b9dc9b
- https://github.com/w8tcha/CKEditor-oEmbed-Plugin/issues/94
