Readers of last night's post were asked to use the information responsibly and told to "stay tuned for the next surprise".
The blogger said addresses and any other identifying personal information had been removed for privacy reasons and users would be able to search only by claim number.
A lengthy blog post outlined the author's views on the EQC and whether the leaked information was commercially sensitive.
EQC spokesman Richard Braddell said the commission was considering its legal options, Stuff.co.nz reported late last night.
He said the matter had been referred to police and the High Court.
The blogger said it was unclear how easy the information would be to download, due to its vast file size.
Meanwhile, Privacy Commissioner Marie Shroff says a wide-ranging review of government agencies' handling of private data may be warranted to restore public confidence following a string of major privacy breaches.
State Services Commissioner Iain Rennie has said he is considering a review after a major investigation into the Bronwyn Pullar ACC privacy breach last year.
But despite a string of further major incidents at the Ministry of Social Development, Inland Revenue, and most recently the EQC, Mr Rennie has said little more about the idea.
Following the EQC breach, Prime Minister John Key said the problems were primarily issues of human error. They did not indicate systemic problems and didn't merit a wide-ranging review.
But yesterday, after appearing before MPs on Parliament's justice and electoral committee, Ms Shroff said such a review "sounds like a good idea to me".
"Potentially we've got to the point where there has been such a lot of public attention and media attention to data breaches that there's a risk of a lessening of public confidence."
Speaking in China, Mr Key said he did not believe a full inquiry into privacy in the public sector was warranted because each of the incidents had been different.
He said the Government had already established a new Chief Information Officer in Colin McDonald and through him it was constantly reviewing "whether the right procedures are in place".
A spokesman for Mr Rennie said Mr McDonald was reviewing the security of publicly accessible state computer systems and information privacy. Once the review was done, consideration would be given to what further work might be required.
