Links to Previous Attacks in UAParserJS Compromise

A very popular npm library called UAParser was compromised this week. The author of the library, Faisal Salman, said:

“I believe someone was hijacking my npm account and published some compromised packages (0.7.29, 0.8.0, 1.0.0) which will probably install malware.”

The compromised package installs a monero miner on Linux and Windows systems. Advisories are available from the package author, GitHub and CISA.

When we analysed the malware – we found that clear links to earlier stages of the attack from an attacker named “wozheqirsplu”, described below.

Malware Analysis

The attacker compromised Faisal’s npm access and updated the npm package.json file to run a file called preinstall.js:

Preinstall.js then determines the operating system:

If it is running on Linux – it then runs

This determines the location of the system, and if it is not in one of the following countries continues to execute:

  • Russia, Ukraine, Belarus or and Kazakhstan

It then downloads the file http://159.148.186[.]228/download/jsextension and executes it. The file jsextension the crypto-currency miner xmrig – set to use the minexmr mining pool with the monero wallet:

  • 49ay9Aq2r3diJtEk3eeKKm7pc5R39AKnbYJZVqAd1UUmew6ZPX1ndfXQCT16v4trWp4erPyXtUQZTHGjbLXWQdBqLMxxYKH

If it is running Windows – it then runs preinstall.bat:

Similarly to the Linux installation – this downloads a copy of xmrig (via curl or certutil) and runs it with the same parameters. The file sdd.dll is detected as a credential theft tool.

Setting up the Attack

The malicious file deployed on Windows machine is served from:

  •  http://159.148.186[.]228/download/jsextension.exe

And has the SHA256 7f986cd3c946f274cdec73f80b84855a77bc2a3c765d68897fbc42835629a5d5.

This file has been seen before.

Back on Wednesday October 20th, Sonatype wrote a blog titled “Newly Found npm Malware Mines Cryptocurrency on Windows, Linux, macOS Devices”. They saw the same file – but back then it was being served from a different server:

  • http://185.173.36[.]219/download/jsextension.exe

Sonatype spotted a malicious user named wozheqirsplu had first created a npm package called okhsa that started calc.exe (Opening the Windows Calculator is a typical first step in testing malicious execution):

They then created a package named klown that impersonated the (later compromised) ua-parser-js library:

The malicious code in this package is an earlier version of the code actually deployed live – it has a couple of small changes such as a different Monero wallet ID:

(Earlier prototype of the code on the left. The right hand side shows the code deployed in the attack)

When Sonatype published their blog on October 20th (two days before the real attack) they noted that – at that point – it wasn’t clear how the attackers intended on deploying their malicious package:

In hindsight – it’s now clear that this was the user wozheqirsplu preparing for their attack.


Assume that any machine that has run compromised versions is compromised, and rotate and credentials or keys on the machine from a separate machine.

When deploying software, check for compromised dependencies as part of any build process.

Indicators of Compromise

citationsherbe[.]at – Note this is also referenced in – we haven’t confirmed the nature of the link yet.



About Cado Security

Cado Security is the provider of the first cloud forensics and incident response platform. By leveraging the scale and speed of the cloud, the Cado platform automates forensic-level data capture and processing across cloud, container, and serverless environments. Only Cado empowers security teams to respond at cloud speed.