It looks like this specific symbol can cause your iPhone Wi-Fi to be totally unusable. Recently, a reverse engineer expert named Carl Schou has discovered that if you use the percentage (%) symbol to name your Wi-Fi Access Point, it can make your iPhone be unusable.
For example, if you named your Wi-Fi as “%scoobydoo%”, this will crash your iPhone Wi-Fi settings. Not only that, but it can also disable Wi-Fi on all iOS devices as well. As for now, Carl Schou founds out that this is a bug that Apple needed to fix it. According to his latest tweet, he confirms that he had to manually modify the iPhone backup network.plist file in order to restore the Wi-Fi settings.
Besides Wi-Fi, even the AirDrop feature also becomes unusable. The reason is that the % symbol creates a bug in the iOS networking stack. This means any feature which uses the networking stack will get affected as well. Apart from that, 9to5 Mac also suggested that the percentage symbol is mostly used in the C programming to format a string variable. Then this variable causes some haywire in the internal library which causes the networking stack to crash.
In conclusion, the percentage (%) is quite dangerous as well to all iOS devices. If you happen to see any Wi-Fi SSID named with a percentage symbol, then don’t ever connect to the Wi-Fi network to avoid this issue. At the moment of writing this article, Apple has not commented regarding this issue. We will try to let you know once we have further updates from Apple.