cromos: Download and Inject code into Google Chrome extensions

by do son · Published November 8, 2017 · Updated November 20, 2017

Cromos

Cromos is a tool for downloading legitimate extensions of the Chrome Web Store and inject codes in the background of the application and more cromos create executable files to force installation via PowerShell for example and also upload files to Dropbox to host the malicious files.

Download extension
Injections
Upload files on Dropbox
Windows infection

Group Policy Object (GPO)

Chrome allows you to add extensions using Windows Group Policy Object (GPO) if you need to force installation on multiple machines just follow the steps in the Chrome Deployment Guide then modify the original extension with few modifications you can publish your extension in the Chrome Web Store requires to pay $5.

Support

If you chose to generate a batch file to force installation the script in powershell that will be downloaded is compatible Windows, 7, 8 10 with versions of powershell >= 3.0

Demo

This is a demonstration of the tool at work in this examples I’m downloading a famous Google extension called G Suite Training on Google Chrome Web Store and injecting a keylogger module.

Installation

$ cd $HOME/
$ git clone https://github.com/fbctf/cromos
$ sudo chmod -R 777 cromos/
$ cd cromos && python setup.py

Usage
Downloading the extension
Usage: python cromos.py –extension {id}

Downloading the extension and loading module
Usage: python cromos.py –extension {id} –load {currency/keylogger}

Build a batch file and upload the files in dropbox
Usage: python cromos.py –extension {id} –build {bat} –token {dropboxToken}

Modules

You can also inject some predefined modules in the background as keylogger, virtual currency.

Module	Description
modules/keylogger	This module captures all the passwords you type in an infected browser over https or not. All you need is to have a php server, for example, to receive the requests get the parameters are email, password, cookies, and userAgent.
modules/currency	This module allows you to mine virtual coins using the coinhive API, you just need to have an account.

Disclaimer

Code samples are provided for educational purposes. Adequate defenses can only be built by researching attack techniques available to malicious actors. Using this code against target systems without prior permission is illegal in most jurisdictions. The authors are not liable for any damages from misuse of this information or code.

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