Happened to me on Firefox 45.0 on Windows.

But when I restarted it gave a popup saying there was an unresponsive script and asking if I wanted to stop it.

Script: data:application/x-javascript;…B9XX0se30sWzMxMV0pKDMxMSl9KTs=:40

Yeah there's a preposterous amount of JavaScript that gets loaded because I'm too lazy to rewrite the interactive graphics. Sorry :(