Windows: Chromium-Based Browser Launched via Script Host with --load-extension

Flags Windows process creation where Chromium browsers are spawned with --load-extension= from common script/LOLBins parents.

FreeReviewedSigma · High · 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

Analysis Detection

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 identifies process creation where a Chromium-based browser executable (Brave/Chrome/Edge/Opera/Vivaldi) is launched with the --load-extension= flag, and the parent process is a common Windows script execution host (cmd.exe, PowerShell, mshta, wscript, cscript, regsvr32, rundll32). Attackers can use custom extensions to gain persistent code execution within the browser environment. The detection relies on Windows process creation telemetry, using parent image names and command-line arguments to match the browser and extension-loading behavior.

Reporting behind it

Related detections9 linkedT1176 — drag to rearrange

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

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Suspicious Browser Extension Sideload From a User Path (via process_creation)

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 via Script Host with --load-extension

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.

suspicious-chromium-based-browser-launched-with-custom-extension-via-load-extens-27ba3207

title: "Windows: Chromium-Based Browser Launched via Script Host with --load-extension"
id: f0f3f9ac-3623-4908-8e6d-65304b6645fc
related:
  - id: 88d6e60c-759d-4ac1-a447-c0f1466c2d21
    type: similar
  - id: 27ba3207-dd30-4812-abbf-5d20c57d474e
    type: derived
status: test
description: This rule identifies process creation where a Chromium-based browser executable (Brave/Chrome/Edge/Opera/Vivaldi) is launched with the --load-extension= flag, and the parent process is a common Windows script execution host (cmd.exe, PowerShell, mshta, wscript, cscript, regsvr32, rundll32). Attackers can use custom extensions to gain persistent code execution within the browser environment. The detection relies on Windows process creation telemetry, using parent image names and command-line arguments to match the browser and extension-loading behavior.
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_susp_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:
    ParentImage|endswith:
      - \cmd.exe
      - \cscript.exe
      - \mshta.exe
      - \powershell.exe
      - \pwsh.exe
      - \regsvr32.exe
      - \rundll32.exe
      - \wscript.exe
    Image|endswith:
      - \brave.exe
      - \chrome.exe
      - \msedge.exe
      - \opera.exe
      - \vivaldi.exe
    CommandLine|contains: --load-extension=
  condition: selection
falsepositives:
  - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_browsers_chromium_susp_load_extension/info.yml
license: DRL-1.1

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