Firefox 31.8.0: Use of Add-On "HTTPS Everywhere 5.1.2" causes 99% CPU utilization

Hallo,

this issue has been mentioned already quite often:
after starting the application Firefox becomes completely unresponsive 
for timespans of say 10 seconds. Then it continues on until the same 
happens again. When it becomes unresponsive, one of the CPU cores will 
show 99% of usage, if you only have/use one core then of course that 
core will show 99% of usage.

As this is really frustrating, I disabled all add-ons and restarted 
Firefox again and again, each time with one additional add-on reenabled.

It now turns out that "HTTPS Everywhere 5.1.2" is the culprit.
If I have it disabled, I don't see this issue, if I enable it, I run 
into the above mentioned problem. This is even true if an "internal" 
webpage like about:addons is displayed in Firefox.

Now, I don't blame Firefox for this error but we would need to find out 
how an add-on executes within the Firefox application process and we 
would need to think about how an add-on can be prevented from 
monopolizing the whole application process.
I don't know if this problem is OS/2 specific but I fear that it is.

Lars