Connecting to a Wi-Fi hotspot with a specific name can cause your iPhone's Wi-Fi functionality to break, and even a reboot won't fix it.
The bug, spotted by reverse engineer Carl Schou and first reported by Bleeping Computer relies on attempting to connect to a hotspot with a specific name. Schou first noticed the issue when trying to connect to his hotspot named with the SSID %p%s%s%s%s%n.
I've tested this with an iPhone running iOS 14.6, and it does indeed disable Wi-Fi, and a reboot doesn't fix it.
So, how do you fix it if, like me, you're relying on your iPhone?
The fix is to go to Settings > General > Reset > Reset Network Settings.
After doing this you will have to reconfigure your network settings.
OK, but how do you prevent this from happening in the first place? After all, little stops pranksters -- or possibly a hacker using this as a vulnerability to do something more malicious -- from setting up Wi-Fi hotspots with this name and no password.
Got to Settings > Wi-Fi and make sure that Auto-Join Hotspots is set to Ask to Join or Never.
Better safe than sorry!
I can also confirm that this does not seem to be an issue for Android users. I tried a number of handsets and they all connected fine.