CVE-2026-16397 Overview
CVE-2026-16397 is a clickjacking vulnerability in the WebExtensions component of Mozilla Firefox for Android. The flaw allows a malicious webpage to trick users into performing unintended actions against installed browser extensions through user interface (UI) redress techniques. Mozilla addressed the issue in Firefox 153 as documented in Mozilla Security Advisory MFSA-2026-68. The weakness maps to [CWE-1021] (Improper Restriction of Rendered UI Layers or Frames). Exploitation requires user interaction on an attacker-controlled page but no authentication. Successful attacks can compromise the integrity of extension-mediated operations on the affected device.
Critical Impact
Attackers can hijack user clicks against WebExtensions in Firefox for Android, causing unintended actions with potential high integrity impact.
Affected Products
- Mozilla Firefox for Android prior to version 153
- Mozilla Firefox WebExtensions component on Android
- Installations running Firefox versions preceding the MFSA-2026-68 patch
Discovery Timeline
- 2026-07-21 - CVE-2026-16397 published to NVD
- 2026-07-22 - Last updated in NVD database
Technical Details for CVE-2026-16397
Vulnerability Analysis
The vulnerability resides in how the Firefox for Android WebExtensions component renders and layers UI elements associated with extension prompts and controls. A malicious page can overlay or frame extension UI so that user gestures registered on the attacker page are actually delivered to the underlying extension surface. This class of flaw is tracked as [CWE-1021], improper restriction of rendered UI layers or frames. The result is that a single tap or click on decoy content triggers a sensitive extension action the user never intended.
Because Firefox extensions on Android frequently expose permissions such as reading site data, controlling tabs, or invoking privileged APIs, an unintended interaction can produce a high integrity impact. Confidentiality and availability are not directly impacted, but downstream actions from a hijacked extension may still expose data. Exploitation is remote over the network and requires user interaction with the attacker-controlled page.
Root Cause
The root cause is insufficient enforcement of framing and overlay restrictions around WebExtensions UI on Firefox for Android. The affected code paths did not adequately isolate extension-owned rendering from content-controlled compositing, allowing attacker content to visually mask or intercept extension interactions.
Attack Vector
An attacker hosts a crafted webpage that positions transparent or misleading elements above extension UI regions. When the user visits the page and interacts with visible decoy controls, the taps are routed to the underlying extension action. No credentials, prior privileges, or local access are required. See the Mozilla Bug Report #2047608 for technical details.
// No verified public proof-of-concept code is available for CVE-2026-16397.
// Refer to MFSA-2026-68 and Bugzilla 2047608 for vendor-supplied details.
Detection Methods for CVE-2026-16397
Indicators of Compromise
- Firefox for Android clients reporting a version below 153 in mobile device management (MDM) inventory
- Unexpected changes to installed WebExtensions, permissions, or extension-managed settings on Android devices
- User reports of extension actions triggered without deliberate interaction
Detection Strategies
- Query endpoint and MDM telemetry for Firefox for Android build strings preceding version 153
- Inspect web proxy or DNS logs for user visits to pages that host suspicious overlay or iframe-heavy content preceding anomalous extension behavior
- Correlate browser crash or extension-error telemetry with visits to untrusted domains to identify potential exploitation attempts
Monitoring Recommendations
- Enable centralized logging of mobile browser versions through unified endpoint management
- Alert when Android devices run out-of-date Firefox builds after the MFSA-2026-68 release date
- Monitor extension install and permission-change events on managed Android fleets for unexplained modifications
How to Mitigate CVE-2026-16397
Immediate Actions Required
- Update Firefox for Android to version 153 or later through the Google Play Store or managed application distribution
- Push mandatory browser updates to managed Android devices through MDM policies
- Notify users to avoid interacting with untrusted pages until the update is confirmed installed
Patch Information
Mozilla fixed CVE-2026-16397 in Firefox 153. Details are published in Mozilla Security Advisory MFSA-2026-68 and tracked in Mozilla Bug Report #2047608. Administrators should verify the installed versionName on Android devices is 153 or higher.
Workarounds
- Restrict or disable non-essential WebExtensions on Firefox for Android until the update is deployed
- Advise users to avoid tapping unexpected UI elements on untrusted websites
- Use MDM policy to enforce automatic updates for Firefox for Android across the fleet
# Verify Firefox for Android version on a connected device via ADB
adb shell dumpsys package org.mozilla.firefox | grep versionName
# Expected output should show versionName=153 or later
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
