A mailing list containing a potential massive quantity of subscribers to News Limited publication Taste.com.au was stolen yesterday by hackers who have already exploited user details.
The attackers swiped an "old version" of the subscriber database and sent spam emails to subscribers.
The company said it was confident its web site was not hacked but News Limited would not provide further details of the incident when contacted by SC, saying only that its "production database" was not affected.
However, in an email to subscribers, News Limited advised users to change passwords for their Taste.com.au account and any other online account which shares the same password.
While Taste.com.au said resetting passwords "may be an overreaction", such advisories have historically been linked to breaches of user account passwords.
News Limited claims Taste.com.au has 2.4 million unique browsers and 23.4 million page impressions each month.
An SC reader had reported the email warning had been flagged as spam. Taste.com.au subscribers are advised to check spam inboxes for the warning email.
A spokesman for the Australian Privacy Commissioner's office said News Limited had not notified it about the breach.