Mac Problem/Virus?

This weird thing has been happening where whenever I open my safari browser it freezes, gives me the spinning rainbow and a ton of these solid grey boxes with drop shadows show up in the bottom left corner of my screen attatched to the safari window. After they're done loading everything works fine. This only happens with safari. Any idea what this is or how to fix it? I updated my laptop a couple weeks ago and it went away but it came back.

There are no known viruses in the Mac world.

Suggest you do a big clean-up. Download and run, if you haven't already, Malwarebytes and Onyx. Clear browsing history and cache.