Browser Extension Exploits: Detection and Mitigation Strategies

Introduction

On September 03, 2024, TrustedSec researchers published a detailed analysis on detecting browser extension exploitation in enterprise environments. Web browsers continue to be a primary target for cyber threats, as tools like Redline Malware or SharpChrome steal sensitive data such as cookies and login credentials. This report provides insight into detection strategies and preventative measures for organizations seeking to combat these browser-related attacks.

Report Overview

The report highlights that attackers often leverage malicious browser extensions or abuse legitimate ones to infiltrate networks and extract sensitive data. Notable attacks include Redline Malware and SharpChrome, which target browsers like Chrome, Firefox, Edge, and Brave to steal credentials. Auditing and logging are essential to detect this type of activity in enterprise networks, but the high volume of browser data can often lead to false positives.

The analysis walks through how to configure auditing to detect malicious extension installation and how to leverage specific event IDs for monitoring. The example focused on Windows Event ID 4657, which detects registry modifications and demonstrates how to identify a potentially malicious extension in logs using Splunk queries. In this case, the LastPass extension demonstrated and simulated an attack scenario.

Example Splunk Query:

This query helps identify when extensions are installed across different browsers, flagging abnormal activity based on predefined parameters like unique process names and registry changes.

Browser-based attacks can result in significant data breaches, especially if attackers access stored credentials or session cookies. This could allow lateral movement within an organization, privilege escalation, or access to cloud-based applications without user intervention. The report notes that this vulnerability, if left unchecked, can lead to more advanced attacks and even widespread system compromise.

Insights and Analysis

The report refers to prior community detection work from TrustedSec and SIGMA detections, reinforcing that multiple layers of defence are necessary to prevent browser abuse. The report emphasizes the importance of building high-fidelity detection rules that minimize false positives and allow security teams to focus on real threats. However, she warns that there is no universal solution for normalizing browser extension identifiers across different platforms.

Organizations are encouraged to limit the browsers and extensions allowed in their environments. In addition to enabling strict access controls, deploying customized Splunk detections and using tools like SharpChrome for simulation can help identify abnormal extension behaviour. IT admins should also enforce policies that prevent users from installing unapproved extensions.

The analysis highlights the risks posed by browser extension abuse and offers practical detection methods to mitigate these risks. Her step-by-step guide provides a framework for identifying and responding to potential threats in real time, helping organizations stay ahead of adversaries. 

Indicators of Compromise (IOCs)

MITRE ATT&CK Mapping

References

When on Workstation, Do as the Local Browsers Do!

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