macOS froze completely while youtube videos were playing

[fabrum]

Hi,

I'm concerned about the security of my iMac. I left it playing a youtube video and somehow it segued to playing other youtube videos even though I block autoplay of videos and audio. Well, when I tried to stop the video or close the Firefox browser then everything was frozen and when I tried to open other MacOS applications such as Activity Monitor to kill Firefox then everything on my Mac was frozen too!

So quickly I pulled plug to my router but that didn't help so I was forced to restart the computer!

I scanned for malware and viruses using Malwarebytes and ClamXAV though found nothing.

The only thing that I could find that might describe this phenomenon was a post from several years ago that Firefox's hardware acceleration might be responsible.

However, I don't see that setting in Firefox.

My macOS and Firefox and everything else are updated fully.

Can someone explain this? Thank you!

 

[DeltaMac]

In Firefox, you can try turning OFF hardware acceleration.
To show that setting, go to Firefox Preferences, then in General, scroll down to Performance, then uncheck the box "Use recommended performance settings". Then you will see the check box for "use Hardware Acceleration when available "

Did you iMac get hot while playing youtube videos? Which iMac do you have?

 

[fabrum]

Okay, thank you! I did not notice if my iMac (late 2015) was hot. However, I did not hear the fan operating. This is the first time that this freezing happened that I'm aware of. However, it's not the first time that Youtube has autoplayed videos even though Firefox is set to block autoplay.

 

[DeltaMac]

Which Late 2015? There's 3...: 21.5-inch, retina 4K 21.5-inch, and Retina 5K 27-inch.
Could be overheating, which should be easy to check on the back, usually in the area of the CPU (back left side), and the fan is just not catching up for a bit, causing the system to lockup.
(Maybe you don't hear the fan because it is not spinning like it should (or maybe the cooling paths inside need to be cleaned out on a 6 year-old computer - might be something to think about, too)
Heat may not be your issue, but if it does, you will feel a lot of heat in the back, and it's something to watch out for, if it happens again.
A freeze-up can also indicate a problem with your boot drive... Do you have fusion drive, or flash storage - or, a hard drive (the 21.5-inch comes standard with a 5400-RPM laptop hard drive, which is sometimes just not a happy beast with the newer macOS systems, and 5 or 6 years can be approaching end-of-life for a mechanical hard drive.