9to5Mac reports on a Wi-Fi bug discovered by Carl Schou: if you join a Wi-Fi network named “%p%s%s%s%s%n” from an iPhone or iPad, it will break both Wi-Fi and AirDrop. Even worse, restarting the device won’t fix it. You’ll have to reset your network settings by going to Settings > General > Reset > Reset Network Settings.
The root cause seems to be Apple failing to sanitize Wi-Fi network names. Those characters preceded by percent signs are commonly used in programming to format variables into an output string. It’s likely that the name gets directly passed into Apple’s code, causing a process crash.
We haven’t seen reports of Wi-Fi networks with this name in the wild yet, but now that the word is out, you can bet that some merry pranksters will take advantage of it. To play it safe, avoid joining any Wi-Fi network with a percent sign in its name.