I have noticed that anything off of the main home page of Huffington Post (i.e. the articles themselves) now cause my CPU fan to rev up and spin loudly. Interestingly, I notice that the font used on these article pages has also changed.
I am using "hardware acceleration" in Firefox, but the problem does appear to be Flash19.0.
When I go into Resource Manager (or Security Task Manager) and sort on CPU, it turns out Flash 19.0 is using 65% of the CPU when I'm on these off-home HuffPost pages.
In contrast, on THIS site (SevenForums) which does not use Flash, everything is quiet and CPU usage is minimal.
So it seems more to be site-design, font used, ads present (or suppressed by AdBlock Plus, etc.), imbedded video links, etc., in other words anything that involves Flash seems to suddenly be burning up the CPU which in turn makes things appear to be very slow. Page scrolling is slow, going to imbedded other links is slow... and I'm sure it's all caused by Flash 19.0.
I wonder if Adobe will fix this, or if we're somehow now doomed. This was not a problem until recently.
I get problems with the site. Unresponsive script and numerous certificate changes. It's heavy with trackers and there are video platforms that use flash.

I have an add on "plugins click to play per element" that only loads flash content for an element when it is clicked on rather than allowing flash content for the whole page and all the domains.

If flash is blocked completely then the site works okay but obviously no flash content will display.
I had to accept numerous certificates. Here's one example.

With click to play per element activated:

These settings are specifically used in my browser but yours will be different.
In about:config "plugins.click_to_play" must be "true".
On about:addons (plugins page) required plugin must be "Ask to activate" if I want to enable the plugin on the page and not the whole website by clicking the "Allow Now" button
in about:config "plugin.sessionPermissionNow.intervalInMinutes" is set to 0 (zero)
Now the interesting part is that the site works without any problem only if:
HOSTS file is the default one.
Any ad blocking is disabled.
Flash plugin detection - when asked choose "Allow Now and Remember" - if I just choose "Allow Now" I get another prompt within seconds.
There are many domains that must not be blocked for the site to work properly.
I don't believe there's a problem with Adobe Flash Player as I can get the website to work by disabling a whole lot of things that block scripts, ads, trackers etc.