FF uses 9% CPU on browser startup

[therube]

(Oh, this is going to be fun.)


FF 61 uses ~9% CPU on browser startup (from Session Restore) - unexpectedly.
NoScript 10.

Restart in Safe Mode & the same.
(Now I have to look & see if I'm Globally Allowed... No I am not, I don't think.
[It is ridiculous that I even have to think about thinking about where I am.])

Anyhow, I take the same exact (literally - for better or worse) Profile, open it in SeaMonkey 2.49.5, install NoScript 5 & Quit.
Decompress sessionstore.jsonlz4 (from FF 61) to sessionstore.json (which should then be usable in SeaMonkey 2.49), open SeaMonkey, & SeaMonkey is using ~2% CPU - with the same browser session.


(NoScript settings in 5, are default, in 10 are probably at defaults, only exception I'm thinking is that Yahoo.com is not allowed.)
I do have other extensions installed in FF - but they are all disabled.
(Mozilla is renowned, currently, for letting malware extensions into their ranks, so no telling what I may have allowed.)


I'm seeing, what I consider, excessive CPU load where I would not expect it.
In particular given that NoScript is installed.
And given that, I would expect to see less CPU usage then when started in Safe Mode, but I'm not.
Tabs are only loaded on demand (by default), so only the focused tab in each window loads (fully).
In most cases (all, probably, with only a google page perhaps being the exception) scripts should be blocked (by default).

Is this a NoScript issue?
Not sure?

Is there a significant difference - using the "same" Profile, so in particular, the same session restore files, between NoScript 5 & NoScript 10 (& given, they are two entirely different browsers).
Yes.


(Clearing Cache [& Offline Website Data] made no difference.)


https://discourse.mozilla.org/
mozilla.org blocked
NoScript 10.1.6.6rc2, loads "blank"
NoScript 10.1.9.1rc1, page displays (some at least, textual data)
NoScript 5, page displays (some at least, textual data)

NoScript 5...
Allow mozilla.org, page then displays "blank"
Allow mozilla-community.org (I wonder who "owns" that, Mozilla or Discourse?), & then page displays fully


I also see persistent I/O in FF, ~160 kB/s not seen in SeaMonkey.
Don't know where it's going? Don't know if it is some kind of loop-back?


So... you say, existing sessionstore.jsonlz4 & a new Profile & NoScript...

~9% & I/O.

Safe Mode: A little lessor CPU & less I/O.


So... you say, get rid of sessionstore.jsonlz4!

Negligible CPU, & still some CPU, ~6 kB/s (though with all FF's spying going on, no telling.)
(Oh, & SeaMonkey, in the full-bore Profile scenario, no I/O.)


That makes no sense (to me).

[therube]

If you want to play (< 200KB), https://www59.zippyshare.com/v/mSRv3vL4/file.html.
(Seems zippyshare isn't that "clean" either, so if you visit, use NoScript.
And it is the orange "Download Now" button you want [in case you see other "download" buttons].)

There is at least some porn in there, a chaturbate ? or some such, but it is not a focused tab.
Otherwise, anything & everything could be in there?
Oh, & "everything" can mean malware too - so if you do this, use NoScript .