Be careful about giving your WiFi network an unusual name — it might create serious headaches for any iPhone users in the household. BleepingComputer and AppleInsider say that security researcher Carl Shou has discovered a naming bug that ‘breaks’ WiFi on iOS devices. Give your network an SSID like “%p%s%s%s%s%n” and your iPhone will lose WiFi functionality. You can get it back by resetting your network settings (Settings > General > Reset > Reset Network Settings), but that’s clearly a pain if you just wanted to avoid using cellular data.

The cause isn’t clear at this point, but BleepingComputer speculated that it might be a string formatting flaw. Simply put, iOS might confuse the % entries with programming commands and variables. Schou noted that he regularly uses names like this to mess with “poorly developed devices.” He tested the bug with iOS 14.4.2, but it was still a problem as of iOS 14.6.

We’ve asked Apple for comment.

Character-related bugs aren’t unheard of. A 2018 bug in iOS and macOS crashed apps using a single symbol. WiFi issues are rare, however, and this glitch would make it relatively easy for pranksters to (temporarily) wreck your phone using public hotspots. While it was already a good idea to avoid connecting to strange hotspots, you’ll have a particularly good reason to resist that temptation while this bug exists.