There are multiple threat vectors when logging onto a typical shared wireless connection. In an open network, aka a wireless network with no password, user traffic is not encrypted and is vulnerable to malicious actors on that network. A second type of network is one with a shared password. Having a shared password is better than no password at all, but since everyone knows the same “secret” it opens a vulnerability where data from your device can be accessed unknowingly and without authorization.
Devices on a flat network (all devices can see other devices) are also vulnerable to malware spreading. So, if John clicks on a phishing email and his device is infected with malware or a virus, it will try to spread to other devices it can see on network and try to infect them. If your device has any vulnerabilities, it could be locked up as well.
Lionstripe fixes these dangers.