The desktop version of the Telegram messenger does not encrypt the correspondence stored on the PC, and this applies to both ordinary messages and 'secret chats'. This flaw was discovered by cybersecurity specialist Nathaniel Sachi.
Text messages from Telegram are stored on the computer in the form of a SQLite database, and although the records contained in it are difficult to read, special software is able to convert them into a more readable format. In addition to the correspondence itself, in the database you can find forwarded photos and phone numbers that can be easily matched with usernames.
Telegram developers have not yet commented on Sachi's find.