@Plan-A̵̛͈̬̥̿͋̓͛̕
QR codes are great, they can hold an amazing amount of information in a very small amount of space. Though as you have said we should always pay attention to what our device asks us and not just accept whatever is offered. If I scan a QR with my phone and it is a vCard my phone will not just add it, it will ask me what I want to do with it. If I am not expecting a vCard I am just going to ignore it. My devices will not just auto join a network. I have to approve any network before it will join it.
Having sane settings on your devices goes a long way. Pay attention to what your device asks you. If it asks if you want to join a network and you did not expect such then refuse. If it asks if you want to create a new contact and you did not expect a vCard refuse. It really is quite simple to avoid being scammed. You just have to pay attention. If your not sure error on the side of caution. Reject it.
There is never a reason to scan random QR codes. If it is not relevant to something you are doing, such as a user manual you received with a purchase has a QR in it. I scan QR codes at work every day for inventory. etc ...
