Client continues to connect to server after canceling on 'Connecting to server' screen

I am on one server and i can read the chat from both of them.

Steps to Reproduce:
1. I started Minecraft 1.8
2. I joined a multiplayer server and while it was loading to found out that i joined the wrong one (CubeKrowd)
3. While it was still loading i cancled
4. I clicked on the right server and joind a world where only a few things where and i was in spectator mode although I should have only been in creative. At that point i could read both chats.
5. I disconnected and logged back in and now the world was normal but still there where both chats

And even if i disconnect again the cubekrowd chat is still there. I tested going to a few different servers but the chat was always there.

When i restarted the game it was gone

 

Being connected to two servers at a time (MC-74984) can be exploited:

• Illegal movement (e.g. "phasing" through blocks), to some extent
• Item transfer when in Creative mode
• X-ray

See https://www.youtube.com/watch?v=EEG_c3ycDg4