Actually it needs to use an HTTP API (because Web Extensions can't send actual DNS requests?): https://github.com/jessejanderson/skylink/blob/a698dd56eda26...
and it looks like it's only resolving domains to DIDs, but not that the DID's owner accepted the domain; so you could make any of your domains point to anyone's DID. The extension would need to use ATP's new protocol to check it.