Thousands of the subscribers to Nine newspapers have had their personal data exposed online in a major cybersecurity breach.
Sixteen-thousand subscribers to the Sydney Morning Herald, The Age and The Financial Review had their names, postal addresses and email addresses left exposed online.
A spokesperson for Nine said payment details and passwords were not affected.
Nine said it was first made aware of the hack to a third-party supplier that had access to subscriber's details by a security researcher.
"We have been made aware by a security researcher that certain personal information held by a third party supplier was not protected to the level of Nine's strict internal data protocols after an unauthorised change," a spokesperson said.
"This included a limited number of The Sydney Morning Herald, The Age and The Australian Financial Review print subscriber records."
The company said there was no breach of its "internal technology infrastructure" and that the data was no longer visible online.
"While there has been no breach of Nine's internal technology infrastructure, Nine treated this matter seriously and worked with the third party to resolve the issue," a spokesperson said.
"The customer personal information that was held by the provider was limited to name, postal address and/or email address.
"The data did not include credit card details or passwords."
The organisation said it was contacting all subscribers who were impacted but the breach could put thousands of users at risk of cyber attacks.
It's the second major cyber breach to be reported in two days, after 9,000 sensitive court files were downloaded from the NSW Courts online registry last week.