FYI, the linked contract is the .eth registrar, which hands out new domains under .eth; ENS itself is here, and its source is here). (deployed LLL version here). The same mitigation would apply, although it could be difficult to eliminate all possible storage of data on behalf of others when it comes to name issuance etc.
Another example of this issue is the DNSSEC Oracle, which allows anyone to submit a proof of existence of a DNS record.