>>Someon+(OP)
Same for me, except on Windows 7. CPU spiked to 100% and I warmed up my hands with the extra heat :). Closing the tab and waiting a minute or so (the usual thing I do for cpu/memory intensive pages like this) didn't work. I had to completely restart Firefox to get it back to normal.
>>Someon+(OP)
I have Firefox 58/64bit/Linux and it slowed down Firefox on my i5 with 16GB ram (2GB free) w/ HDD for about 1 second... it didn't lock it up because any action that I did on firefox was slowed down by about 1 second... other programs seemed fine too.