Details of up to 40,000 Acer customers were exposed to hackers using a username and password the IT company's staff posted to a support forum three years ago.
Acer was not immediately available for comment.
A group calling itself the Pakistan Cyber Army accessed names, phone numbers, software serials, home and email addresses of Acer customers stored in Excel spreadsheets.
The group used access credentials posted on the support forum, according to the Hacker News and obtained FTP server access.
From there it downloaded 40,000 customer details from an unencrypted zip file dubbed "Country Wise Customer Data".
And it accessed Acer source code.
Hackers said they would publish the details on file-sharing networks.
Acer support staff posted the FTP access credentials for Acer Europe on a company support forum in January, 2008. It appeared the details were used to allow customers to download a software hotfix.
Acer took the FTP server and support forum offline.