However, the spokesperson could not confirm which agency's data was involved because of the responsibility to protect privacy. The Herald understands it was a High Commission.
"As with any breach, Quinovic will need to investigate to fully ascertain the size and scope of the breach," the spokesperson said.
"Our focus in these early stages is to provide agencies who have experienced a breach with advice on how minimise the harm caused by the breach on the individuals impacted."
Sheridan said the Commissioner has provided guidance to avoid such an incident happening again, which Quinovic would be following.
Quinovic has offices across the country, including four in central Wellington.
Established in 1988, the company has managed properties for more than 30,000 owners.
But over the years the company has courted its fair share of controversy. Its Te Aro franchise in Wellington drew the ire of renters' associations when it posted an ad on its Facebook page stating: "Your tenants may hate us. You will love us!"
Another ad at the time showed a photo of two people clinking glasses underneath a tagline that asked landlords if they were financing their tenants' social lives.
The ads were eventually pulled after Quinovic's head office intervened, saying they did not conform to the company's "brand standards".
The same franchise was accused of using fake reviews on its Facebook site.
Te Aro had a "5 out of 5" rating on Facebook, despite its positive reviews coming from landlords and tenants with profiles that either have no photo or photos appearing elsewhere under different names or as stock images.
An investigation concluded the reviews were in fact fake but there did not appear to be any link between the Facebook accounts and any known property owner or tenants on Quinovic's database.
