The Information Security logo has been replaced by the Server Fault one in all of the three top left drop down menus:
The Server Fault logo seems to be the default blue box that is used for sites in beta. I suspect someone is already on this, and fixing it, but in case not I thought I should leave a note here.
EDIT: Since apparently this doesn't happen to everybody, here is some more info. I have tried on different devices on different networks (but all in the same country). I have refreched multiple times, and cleared the cache. The issue still persists. (Perhaps it is local to a specific CDN exit node? I have only tried from Sweden.)
And apparently our logo is not the only one messed up: