One of the major competitors in the messenger market, Telegram was recently reported to leaks internet addresses of users. The flaw was discovered in the desktop app by a security researcher Dhiraj Mishra. Bug report shows that peer to peer calling(an exclusive feature by Telegram), revealed IP addresses for both users communicating, which may, in turn, allow attackers to take control over your network, or become an easy target.
Mishra reported the issue to Telegram, and as a part of bug bounty program, he received a sum of about €2,000. This issue has been fixed in 1.3.17 beta and 1.4 versions. Now you can either disable peer-to-peer calling entirely or limit it to your contacts.