Sounds horrible......"Firefox can deliver on-screen notifications even when that site isn’t loaded"

[dixiegrrrrl]

Why would I want this feature ???

Starting with version 44, Firefox can deliver on-screen notifications even when that site isn’t loaded. Using the Push API, a W3C standard, Firefox receives a push message and can show notifications (if permitted by the user) at any time.

Sites can also use Push to update data in the background even without showing you a notification.

If you already gave permission to a site to send notifications, the site will also be able to use the Push API.

You can choose whether or not to give permission for a site to send you notifications by following these instructions:

https://support.mozilla.org/en-US/kb/push-notifications-firefox?as=u&utm_source=inproduct#w_upgraded-notifications

[friendly_iconoclast]

1. Where's the problem? If you don't opt-in beforehand, you won't get push messages or updates

*Only* sites that you allow beforehand to send notifications can do this
From the page you linked to:

How do I revoke Web Push permissions?

Web Push is always opt-in in Firefox. A site cannot send you push messages without your permission. To stop a specific site from sending you push messages:

Go to the Firefox menu New Fx Menu and select Options.
Select the Content panel and click the Choose… button under Notifications.
Select the site.
Click Remove Site.

To stop all sites from sending you push messages, follow the above steps except, instead of selecting a specific site, click Remove All Sites. Websites will not be able to send you messages and will need to ask your permission to send them in the future.

[dixiegrrrrl]

3. Tis the ability and willingness of a browser to allow other sites access to your computer...

for now, yes we can opt out.
Down the road, you never know.

and, when I did click on the permission box, one site was already there, I had to remove it.
do notice the instructions....
To stop all sites from sending you messages....you have to click Remove all Sites.
I read that as saying you have to opt OUT to stop all sites from sending messages, not opt in.

Altho, the truth is, you have to opt out and you CAN opt in, by clicking a werbsite's icon.

[Downwinder]

2. Now I can get Valentines when I am not on DU.