Here's the rule-of-thumb, these small time sellers are interested in sales, not pwning you. They may counterfeit but they aren't going to bother installing backdoors nor are they sophisticated enough to do so. They may inadvertently do so out of incompetence but that was not their goal.
People who really do want to pwn you wear suits and sit in large offices and they will get you to do it voluntarily by signing a EULA.