What exactly is this anyways? Mind showing us the full screenshots? I know that you took them as indicated by the chat logs shown in the last screenshot. Could just be some stupid new feature since I haven't been keeping up with Minecraft updates for the past year or two but that sure as hell looks like a hacked client to me.
It was a hacked client, of which I don't use on OSB, I was asked to change client and I have. I do use my hacked client when playing with staff on other servers and they are aware that I do not use it on OSB on purpose. It is easy to forget to change clients when switching servers.