Extreme CPU usage on downloads from mega.co.nz

Hello,

I was downloading a 500 MB file from mega.co.nz and when it reached 99% my CPU gone at 100% for several minutes. I checked the temperature sensors it was 100ºC, I quickly killed firefox.exe (Tor Browser) and CPU usage got down to 1% and temperatures to be more relieving 60ºC.

Then I quickly googled regarding the so-called javascript security improvements, since I've read about them in the past somewhere, and saw this: https://lists.torproject.org/pipermail/tor-bugs/2013-October/048908.html

For the record I run NoScript with default to disable all scripts and only allow them temporarily on trusted sites. Also I am running mega.co.nz with their browser extension and download speeds reach up to 1.5 MB/sec which is quite fast than what I was used to in TOR.

Back the subject, I've retried after enabling those settings manually: javascript.options.ion.content javascript.options.baselinejit.content javascript.options.asmjs javascript.options.typeinference

And download went much better and hit 100% in the expected time with max 15% CPU usage.

I think there should some sort of warning about this issue somewhere. If I wasn't around, I'd expect having my CPU/Motherboard burnt out.

Software versions: Microsoft Windows 7 Mozilla Firefox ESR 24.8.0 Tor Browser Bundle 4.0-alpha2 MEGA 2.0.179

Regards, NewEraCracker

Trac:
Username: NewEraCracker