Windows Chromium-Based Browser Launched With --load-extension Flag

Alerts when a Chromium-based browser starts with --load-extension= to load a custom extension.

FreeReviewedSigma · Medium · v2

Product: windows
Category: process_creation
Author: Aedan Russell, frack113, X__Junior (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2022-06-19
Updated: 2026-07-31

ATT&CK techniques

Persistence

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1176Software Extensions
- T1176.001Browser Extensions
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags process creation where a Chromium-based browser (Chrome, Edge, Brave, Opera, or Vivaldi) is executed with a command line containing the --load-extension= flag. Attackers can use this behavior to force the browser to load attacker-controlled extensions at runtime, which may enable persistence or data access. The detection relies on Windows process creation telemetry capturing the image path and full command line.

Reporting behind it

Related detections9 linkedT1176 — drag to rearrange

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Suspicious Chrome Remote Debugging Port for Browser Session Theft

Suspicious Microsoft Edge Unpacked Extension Load via UNC6692 Edgecution

Malicious Chrome Extension Sideload via --load-extension from User-Writable Path (via process_creation)

Suspicious Edgecution Malicious Extension Load via Headless Edge (via process_creation)

Malicious Chrome Relaunch Hijack by FlutterShell Backdoor on macOS (via process_creation)

Windows ChromeLoader Execution via Scheduled Task and Hidden PowerShell Launch

Windows Chromium-Based Browser Launched With --load-extension Flag

Pivot detection · T1176 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-chromium-based-browser-launched-with-load-extension-custom-flag-88d6e60c

title: Windows Chromium-Based Browser Launched With --load-extension Flag
id: 2c483492-ca0c-48f7-9375-414b189d35cd
related:
  - id: 27ba3207-dd30-4812-abbf-5d20c57d474e
    type: similar
  - id: 88d6e60c-759d-4ac1-a447-c0f1466c2d21
    type: derived
status: test
description: This rule flags process creation where a Chromium-based browser (Chrome, Edge, Brave, Opera, or Vivaldi) is executed with a command line containing the --load-extension= flag. Attackers can use this behavior to force the browser to load attacker-controlled extensions at runtime, which may enable persistence or data access. The detection relies on Windows process creation telemetry capturing the image path and full command line.
references:
  - https://redcanary.com/blog/chromeloader/
  - https://emkc.org/s/RJjuLa
  - https://www.mandiant.com/resources/blog/lnk-between-browsers
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_browsers_chromium_load_extension.yml
author: Aedan Russell, frack113, X__Junior (Nextron Systems), Huntrule Team
date: 2022-06-19
modified: 2023-11-28
tags:
  - attack.persistence
  - attack.t1176.001
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith:
      - \brave.exe
      - \chrome.exe
      - \msedge.exe
      - \opera.exe
      - \vivaldi.exe
    CommandLine|contains: --load-extension=
  condition: selection
falsepositives:
  - Usage of Chrome Extensions in testing tools such as BurpSuite will trigger this alert
level: medium
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_browsers_chromium_load_extension/info.yml
license: DRL-1.1

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