For those that don't know, Firefox has in-built support for automatically rejecting cookies and blocking the cookie banners from popping up.

To enable this feature, go to about:config, and perform the following:

• change cookiebanners.service.mode from 0 to 2

To have this functionality in Private browsing mode, you should also:

• change cookiebanners.service.mode.privateBrowsing from 0 to 2.

All Power to the People!

edit: (credit for this information goes to this lemming). Apparently, mode 2 means reject all or fall back to accept all if there is no Reject All button. Mode 1 only hits a Reject All button if available but ignores others.