Back in February 2018, Apple iPhone users running iOS 11.2.5 noticed that their phone would crash whenever they received an iMessage containing a certain character from the Telugu language. The language is spoken in certain areas of India, but this one particular character could not be rendered by the iPhone at the time which is why it crashed the phone.
Something similar is happening now, according to some Reddit users (via AppleInsider) and it affects those using an iPhone or iPad running iOS 13 or iPadOS 13 respectively. A notification containing the Italian flag and a specific character from Pakistan's Sindhi language will cause the device to crash whenever it appears. It apparently first surfaced in the Telegram messaging app and has made its way to Twitter. You might consider turning off notifications for any messaging app on your iPhone or iPad by going to Settings > Notifications. Scroll down to any messaging apps, tap on the name, and toggle off notifications. Once Apple sends out a software update to fix the bug, you can turn these notifications back on. You also might want to consider disabling message previews in notifications.
Back in 2018, Apple worked pretty quickly to fix the problem. We do expect iOS 13.4.5 to be disseminated soon and hopefully, it will exterminate this bug.