CVE-2024-8382: Mozilla Firefox Information Disclosure Flaw

CVE-2024-8382 Overview

CVE-2024-8382 affects Mozilla Firefox, Firefox ESR, and Thunderbird. Internal browser event interfaces were exposed to web content when privileged EventHandler listener callbacks ran for those events. Web content could not invoke these interfaces with elevated privileges. However, the presence of those interfaces revealed that certain browser features had been used, such as when a user opened the Dev Tools console. This information disclosure issue falls under [CWE-273] (Improper Check for Dropped Privileges).

Critical Impact

Web content can detect privileged browser activity, including Dev Tools console usage, enabling targeted fingerprinting and follow-on attack staging.

Affected Products

• Mozilla Firefox versions prior to 130
• Mozilla Firefox ESR versions prior to 128.2 and prior to 115.15
• Mozilla Thunderbird versions prior to 128.2 and prior to 115.15

Discovery Timeline

• 2024-09-03 - CVE-2024-8382 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2024-8382

Vulnerability Analysis

The flaw resides in how Firefox handles EventHandler listener callbacks executed in a privileged context. When a privileged callback ran in response to an internal browser event, the associated event interface objects became reachable from regular web content. Web pages could not call these interfaces with elevated privileges, so direct code execution was not possible through this path. However, the mere reachability of the interfaces leaked the fact that a privileged feature had been invoked.

A practical example involves the Dev Tools console. When a user opened the console, privileged event listeners fired and exposed internal interfaces to the page DOM. Scripts running in the page could then detect the console opening, enabling anti-analysis behavior or targeted exploitation paths.

Root Cause

The root cause is improper isolation between privileged (chrome) and unprivileged (content) JavaScript contexts during event dispatch. The browser failed to fully strip or hide internal interface objects when transitioning across the privilege boundary, leaving residual references that content scripts could enumerate.

Attack Vector

Exploitation requires user interaction with a malicious or compromised web page. An attacker hosts JavaScript that probes for the presence of internal event interfaces and reacts when they appear. The technique is most useful for fingerprinting browser state, evading developer inspection, and chaining with other vulnerabilities that depend on a known browser context. See the Mozilla Bug Report #1906744 for technical details.

Detection Methods for CVE-2024-8382

Indicators of Compromise

• Browser processes running outdated Firefox versions below 130, Firefox ESR below 128.2 or 115.15, or Thunderbird below 128.2 or 115.15.
• Web pages performing repeated property probes against window and global event objects looking for chrome-only interface names.
• Anti-debugging JavaScript that alters execution flow when Dev Tools are opened.

Detection Strategies

• Inventory installed browser versions across endpoints and flag hosts running Firefox or Thunderbird builds released before September 2024.
• Inspect proxy and DNS logs for repeated visits to pages that serve heavily obfuscated JavaScript with browser feature-detection patterns.
• Use EDR telemetry to correlate browser child-process activity with subsequent suspicious network connections or file writes shortly after Dev Tools usage.

Monitoring Recommendations

• Track Firefox and Thunderbird version distribution through software inventory feeds and alert on unpatched installs.
• Monitor web filtering logs for traffic to domains hosting browser fingerprinting frameworks.
• Subscribe to Mozilla advisory feeds, including MFSA-2024-39, MFSA-2024-40, and MFSA-2024-41, to track related Mozilla patches.

How to Mitigate CVE-2024-8382

Immediate Actions Required

• Update Firefox to version 130 or later on all managed endpoints.
• Update Firefox ESR to 128.2 or 115.15, depending on your deployment channel.
• Update Thunderbird to 128.2 or 115.15.
• Apply Debian package updates referenced in Debian LTS Announcement #12 and Debian LTS Announcement #25 for Linux fleets.

Patch Information

Mozilla addressed the issue in Firefox 130, Firefox ESR 128.2, Firefox ESR 115.15, Thunderbird 128.2, and Thunderbird 115.15. Patch metadata is documented in MFSA-2024-39, MFSA-2024-40, MFSA-2024-41, MFSA-2024-43, and MFSA-2024-44.

Workarounds

• Enforce enterprise update policies through Firefox ESR managed deployments to guarantee timely patch rollout.
• Restrict JavaScript execution on untrusted sites using browser security policies or content filtering until patches are deployed.
• Advise users to avoid opening Dev Tools on untrusted pages, since the exposure is triggered by privileged browser feature usage.

# Verify installed Firefox version on Linux endpoints
firefox --version

# Example apt upgrade for Debian-based systems
sudo apt update && sudo apt install --only-upgrade firefox-esr thunderbird