Blue and white rectangle

Question

I just restarted my MacBook Pro and I am now getting a blue and white rectangle near the top right corner of my screen. Does anyone know what this is or what is causing it?

MacBook Pro Retina 15-inch, Late 2013, Version 10.11.3.

After restarting my laptop again, the box was not there immediately, but showed up before everything was fully loaded in a slightly different location.

I am unable to click on the box, and trying to drag it just creates the regular selection box as if nothing is there.

Update: I ran Apple's diagnostics and it claimed there is nothing wrong with the machine itself.

Update 2: I attempted to restart my machine into safe mode a couple times but it did not seem to work. It looked like a normal load sequence, just hanging before asking for my login credentials. However, after a regular login, I no longer seem to have this issue. Hopefully it stays this way.

Answer 1

Here's a list of steps to possibly resolve your problem:

1. Reset Finder: This is a basic step, just open up Force Quit Applications by calling ⌘-⌥-esc and then press finder and reset it.
2. Open Terminal and enter the command killall Finder. If it goes away then it's a problem with finder.
3. Open Activity Monitor: If there is anything irregular open in activity monitor just close it. However, be very careful with Activity Monitor. It's easy to close something that will crash your machine.