I've had this happen a few times getting interview requests from Indian recruiting firms. It sounded familiar. You go through a screening, then get passed onto the "code challenge" part. You have to download a GitHub file and then work on it, check it back in and push it so they can examine what you did.

Twice I scanned the file after downloading it to a sandbox and twice it found malware that would've been installed.

While this is by far the worst case of this happening, I've read at least a half dozen other accounts of recruiting companies attempting to install malware through the same process. I'm not saying the person should have known, but it's scary this is becoming more and more common.