Australia Post has withdrawn its Click and Send online service after a security flaw was uncovered that could expose the details of random customers.
News.com.au reported the glitch, which allegedly enabled users to expose others' details by altering a shipping ID number that appeared in the URL of a completed transaction.
Click and Send could be used to prepare postage documentation online, such as customs declaration forms, and pre-pay postage.
The postal service said in a statement that Click and Send had been "temporarily suspended due to a system error".
"As a result, the site has been temporarily deactivated, as our team works to ensure the security of the system for all customers," Australia Post stated.
"We hope to have the service back up and running as soon as possible. Australia Post would like to reassure Click and Send customers that at no stage were their financial details compromised."