There are 3 open security issues in buster.
2 issues left for the package maintainer to handle:
Telegram Desktop through 2.0.1, Telegram through 6.0.1 for Android, and Telegram through 6.0.1 for iOS allow an IDN Homograph attack via Punycode in a public URL or a group chat invitation URL.
Telegram Desktop through 2.1.13 allows a spoofed file type to bypass the Dangerous File Type Execution protection mechanism, as demonstrated by use of the chat window with a filename that lacks an extension.
You can find information about how to handle these issues in the security team's documentation.
1 ignored issue:
Telegram Desktop before 1.5.12 on Windows, and the Telegram applications for Android, iOS, and Linux, is vulnerable to an IDN homograph attack when displaying messages containing URLs. This occurs because the application produces a clickable link even if (for example) Latin and Cyrillic characters exist in the same domain name, and the available font has an identical representation of characters from different alphabets.