Check your browser configuration and disable web notifications for the sites in question. Web notifications are a W3C standard that allows websites to send push notifications to your browser. Presumably, everybody who reviewed it was a naive idiot.
With Firefox/Waterfox there is an about:config setting that disables the whole thing (dom.webnotifications.enabled). In Chrome you can search settings for "Notifications" which should take you to the place which has the allowed sites, blocked sites, and the toggle for whether websites can ask to pester you.