Comment 3 for bug 1497210

As pointed out in the description, ad blockers are usually implemented as browser extensions. Oxide (the web engine) doesn’t have an extension mechanism, and it’s not part of its design goals to grow one. So unless we fork an existing open source ad blocker codebase to work only with the UserScript mechanism that oxide exposes, we can’t really implement such a feature.
Keeping the bug open though, as it’s a valid feature request.