Current version
2.6
What changed
Viber forwarding has been removed - Viber does not allow posting into a private channel or group, so the option could never be completed. Telegram forwarding and the web portal are unchanged.
Latest release
What is published right now.
This page reads the same release file the app's own updater reads, so it is never out of step with what your phone will download.
How you get this
You do not need to download anything from here. The app checks for new versions daily, downloads them in the background and holds them ready — installing takes one tap, whenever suits you. Android confirms every install, and refuses any build not signed with the same certificate as the app already on your phone.
Only the current release is listed. Earlier release notes were not kept in a form this page can read, and inventing them would be worse than leaving them out.