The Australian Competition and Consumer Commission (ACCC) has apologised after the addresses of subscribers to some of the ACC's information alert services were published online.
In a statement, the consumer watchdog said the Recalls Australia, Product Safety Australia, SCAMwatch and the ACCC Public Registers websites were affected.
"They were not indexed by search engines or linked from a Web page on our sites. They could only be found if specific URLs were tried," the ACCC said.
It said that it was "not yet clear" how many users had been affected or how long the addresses had been accessible.
According to the watchdog, it resolved the issue "as soon as it became aware of it" and to prevent further access to the email addresses.
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The ACCC added that it was investigating the issue and had reported the data breach to the Office of the Australian Information Commissioner (OAIC).
"The ACCC takes the issue of privacy, including any breaches, very seriously and apologises to affected users. The ACCC has no further comment at this time," it said.
An OAIC spokeswoman confirmed that it had been in contact with the ACCC, which had provided some information about the breach.
"The OAIC is considering this information to determine if any further action is required," the spokeswoman said.
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