I had a cloud service that I built uploaded to a private repo so that I could get a second opinion from some other developers I knew. The code itself was proprietary, as in, unlike my other projects, I have never given anyone a license to use/copy/modify/etc any of the code, but a few months ago I found my repo reuploaded with no changes except that the person who reuploaded it had added their own copyright notices to it… normally I would be fine with this, especially in my projects where I include a license that allows this, and if they had done this without including their own copyright notices I doubt I would’ve cared, but how they did this really annoys me. Back when I found it I submitted a pull request to their repo which just removed the infringing code, but after a few months, during which time I also tried to contact the author on other platforms, they’ve just ignored the pull request, so what else can I do?
You can ask Github to remove the code. There’s a lot of legal stuff involved, so I’m just going to point at the relevant documentation: