CVE-2023-25743
📋 TL;DR
This vulnerability in Firefox Focus allows malicious websites to spoof browser interface elements by entering fullscreen mode without proper user notification. Attackers could trick users into interacting with fake browser chrome, potentially leading to credential theft or malware installation. Only Firefox Focus versions before 110 and Firefox ESR before 102.8 are affected.
💻 Affected Systems
- Firefox Focus
- Firefox ESR
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers could create convincing fake browser interfaces to steal credentials, install malware, or trick users into performing unintended actions by mimicking legitimate browser controls.
Likely Case
Phishing attacks where users are tricked into entering credentials into fake browser interfaces or clicking malicious elements disguised as legitimate browser controls.
If Mitigated
Users would see proper fullscreen notifications and could exit fullscreen mode to verify browser authenticity, preventing spoofing attacks.
🎯 Exploit Status
Exploitation requires user to visit a malicious website, but no authentication or special conditions are needed beyond that.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox Focus 110, Firefox ESR 102.8
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2023-05/
Restart Required: Yes
Instructions:
1. Open Firefox Focus app store (Google Play Store or Apple App Store). 2. Check for updates. 3. Install Firefox Focus version 110 or later. 4. Restart the browser.
🔧 Temporary Workarounds
Disable JavaScript
allPrevents malicious websites from executing JavaScript that triggers fullscreen mode spoofing.
Settings → Privacy & Security → Disable JavaScript
Use Regular Firefox
allSwitch to regular Firefox browser which is not affected by this vulnerability.
🧯 If You Can't Patch
- Avoid visiting untrusted websites with Firefox Focus
- Educate users to look for fullscreen notifications and exit fullscreen mode if browser interface looks suspicious
🔍 How to Verify
Check if Vulnerable:
Check Firefox Focus version in app settings. If version is below 110, the browser is vulnerable.Check Version:
Open Firefox Focus → Settings → About Firefox FocusVerify Fix Applied:
After updating, verify version is 110 or higher in app settings.📡 Detection & Monitoring
Log Indicators:
- Unusual fullscreen mode activations
- User reports of suspicious browser interfaces
Network Indicators:
- Connections to known malicious domains that could host spoofing pages
SIEM Query:
Not applicable for mobile browser vulnerabilities🔗 References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1800203
- https://www.mozilla.org/security/advisories/mfsa2023-05/
- https://www.mozilla.org/security/advisories/mfsa2023-06/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1800203
- https://www.mozilla.org/security/advisories/mfsa2023-05/
- https://www.mozilla.org/security/advisories/mfsa2023-06/
