I've seen blatant cases as well. There was a github repo where someone was sharing their notes on performance engineering, and there were tickets from people thanking them for their amazing work. Except these notes were literally copy-n-pasted pages from my systems performance book. It's weird to find all these messages from people thanking someone else for the work I did.

When I contacted them to ask how they thought it was ok to republish my work like this (I was giving them a chance to explain), they just took it all down.