One of the malware collections on GitHub is this repository. I strongly recommend that you do not open any of the samples here on your host computer, as they are all dangerous and malicious. These samples should not be even used for pranking your friends. Playing with aforementioned samples may lead to irreversible consequences, which may affect anything from your personal data up to passwords, credit cards and your computer/laptop.
If you want to test these samples, then please test them on a safe environment like a virtual machine, you can use VMWare or VirtualBox. Do not use shared folders and disconnect your internet in the virtual machine so the malware samples do not spread to your PC (if they can).
I am not responsible for any damage caused by my repository and your negligence in general.
There are tons of sources from where I get these malware samples which include other malware repositories.
Please use the issues tab for reporting issues related to the repository (including malware addition requests will go here). For adding new malware that you have, please use the issues tab. Do not upload the malware directly, instead provide a link to the malware.
This repository is currently in development. I am adding more samples, it will take some time.