Hikka is a Telegram userbot. A vulnerability affects all users of versions below 1.6.2, including most of the forks. It allows an unauthenticated attacker to gain access to Telegram account of a victim, as well as full access to the server. The issue is patched in version 1.6.2. No known workarounds are available.
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.