The Telegram Bot & Channel plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Telegram username in all versions up to, and including, 4.1 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

Telegram Desktop (aka tdesktop) 1.3.14, and Telegram 3.3.0.0 WP8.1 on Windows, leaks end-user public and private IP addresses during a call because of an unsafe default behavior in which P2P connections are accepted from clients outside of the My Contacts list.