Many of the risks have already been covered in the post by Mayank Sharma. I just want to add on this by saying that wifi clients trust relationship with the access point is highly influenced by signal strength, i.e. the proximity between client and access point.

Such is the case when your laptop with wifi enabled and set up to automatically connect (its default setting), when put near an open access point will always attempt to connect to that station.

You should always be vigilant about this behavior as in many cases it happens without any user interaction. The best way to prevent this is to configure your client to always connect only to preferred access point (you can do that in the settings options)![Something similar to what is given over here (notice the "Ask to join" check box)][1]


  [1]: https://i.sstatic.net/k3Ji8.png