Webpush notifications in firefox - howto get rid of them

Visited a site and after that I got small notifications of that site while browsing on others. Never experienced that before; no new extensions that could explain it. This is the explanation :

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

1. Click the icon to bring up the Control Center.
2. Click the menu next to Permissions and choose a notification option: Always Ask, Allow, or Block. 

*The strange thing that I never gave permission to do this on this site except for accepting cookies. 

You have to visit the site that annoys you and look at the top left next to the email address to find the I icon. Click on the I and then on the right arrow button and then on More Information at the bottom. Then you will see a few tabs and can you choose the permission tab and  change allow to block.