A major example of how Telegram's opt-in secret chat encryption has gone seriously wrong before: https://words.filippo.io/dispatches/telegram-ecdh/.
The practical near term threat is for the vast majority of chats without end-to-end encryption: 100% of Telegram group chats and the regular 1-to-1 chats.
@GrapheneOS "The current consensus seems to be that the latest version is not broken in known ways that are severe or relevant enough to affect end users, assuming the implementation is correct. That is about as safe as leaving exposed wires around your house because they are either not live or placed high enough that no one should touch them."
#Telegram #TelegramSecurity #MTProto