How to completely disable push notifications in Firefox?

From further research, I discovered that you have to go into the about:config interface. HERE BE DRAGONS! (1) Or if you use the American locale, Your warranty might be voided (2)

I changed four settings to FALSE:

• dom.webnotifications.enabled
• dom.webnotifications.serviceworker.enabled
• dom.pushconnection.enabled
• dom.push.enabled

(1) Here be dragons:

(2) This might void your warranty:

With the release of Firefox 59, we can now disable push notifications using the default Options page.

The official release notes for Firefox 59 described the modification:

Added settings in about:preferences to stop websites from asking to send notifications

You can configure this option in the following manner:

1. Navigate to the about:preferences page
2. Click on Privacy & Security on the upper-left
3. Scroll down to the Permissions section on the right

4. Click on the Settings... button associated with Notifications

   

5. In the subsequent window check the box to Block new requests asking to allow notifications

6. Click the Save Changes button