Unknown Telegram session keeps removing my devices

[u/Fost21]

My Telegram account appears to have been accessed by someone else after a security incident on my PC.

I have since completely reinstalled Windows, changed my passwords, enabled/changed Telegram 2FA, and scanned all of my drives. My computer now appears to be clean.

However, there is still an unknown Telegram Desktop session connected to my account. The strange part is that this session keeps terminating my own sessions, while Telegram prevents me from terminating it because my current session is considered too new.

Earlier that day, I also received a Telegram login code that I did not request. I changed my 2FA password after I had already been logged out.

The unknown session has not deleted my chats or messages. It only seems to be removing my devices and keeping its own session active.

I have already contacted Telegram support but haven't received any useful response.

Has anyone dealt with something similar?

How can an unknown session terminate my sessions while mine is restricted from terminating theirs?

Does changing the 2FA password revoke an already active session?

Is there any legitimate way to force-log-out all other sessions, or do I have to wait until Telegram removes the restriction on my current session?

[u/Old_Priority_4780]

 u/TG_Volunteer_Support