A security researcher by the name of Carl Schou has announced via Twitter that iOS device WiFi capabilities could be disabled when they come into range of a specific Wi-Fi name.

An iPhone that comes into Wi-Fi networks with the %n, %p and %s character will find itself unable to use Wi-Fi or related features. This problem could persist even if the user reset his or her device’s network settings when they come into range with the network name ‘%secretclub%power’
The bugs identified exploit a string format coding error in iOS networking stack. Schou revealed that even a reset may not be enough to restore Wi-Fi functionality and the user may need to do a hard device reset.
iOS users are not recommended to try this bug error for themselves and wait until a fix or a software update appears. It’s also recommended to disable Wi-Fi while outside by going to the iPhone’s Settings.