Is it safe to buy EA from folks you do not really know ?
Can the EA that you buy from some one else online be used to hack into your PC ?
Yes, technically it is possible. If I had the DLL enabled, I could read files from the computer, save files to your computer, connect via internet to any server, and run executables on your computer. But this way can behave all applications, so you must decide, if the author is a trustful commercial seller or a hidden-identity person with no serious business record behind.