As an example of this, I believe SexyCyborg got in trouble for reporting on leaks via people’s 3rd party Chinese language keyboards. So her theory is that the keyboard apps people had installed leaked data when Hong Kong protesters were communicating with the press, rather than the actual Signal app. But… as stated above, people have to take responsibility for their device and in this case, they had chosen to install apps with leak issues into the communication process.
I have literally never downloaded pirated software since OS 9 went away and OS X became a thing. Open up your task manager and look at how many processes there are (Window, Mac or Linux) and ask yourself if you’re going to notice the one extra process that is out of place.
As for files with extra extensions, this is why you should always set Explorer/Finder/whatever to show all file extensions the very first thing, regardless of what OS you’re running too.