Appearing as someone else?

So,

I've been off of this for a while and came back to see what's changed only to find that somehow I've been logged in as someone else?

I refreshed the page and my account has come up now but I'm a bit concerned that this has happened and was wondering if it was something you guys were aware of? There's some very private information in my account not visible to others and I wanted to ensure that no-one else is able to see that information.

Have included a picture: (Snipping tool wasn't working so I had to use my phone)
ZbyvsqW.jpg