The latest bug, discovered by Italian blog Mobile World, is focused on a single character of a local Indian language (Telugu), which once typed on any iOS device can cause it to misbehave, crash, or even end stuck in a bootloop.
If a user were to open any conversation in a text-based app like WhatsApp, Twitter, or Facebook Messenger, and type the character, the app will crash, and it will keep force closing each time you try to re-open it.
As The Verge reported, the bug also afflicts other third-party applications, such as Gmail and Outlook for iOS, while others like Skype and Telegram seem to be unaffected.
If someone else were to send the character as a text, the notification snippet containing the character could also freeze or restart the entire iOS springboard by itself; Mobile World suggests that, in that case, users wait for the device to reboot itself automatically, because forcing it to do so may result in a bootloop.
Mobile World also says that the bug afflicts platforms beyond iOS: watchOS and macOS apps like Notes, Safari, and the App Store all reportedly crash as soon as the infamous character shows up.
A recent community bug report over at OpenRadar confirmed as much: "Trying to insert [the symbol] in any system text renderer like TextField, Label, TextView [makes devices] always [...] crash."
The only safe operating system seems to be iOS 11.3, which is however only publicly available in beta form. You can watch Mobile World's full demonstrative video (in Italian) below.