Customers who had recently purchased a Woolworths voucher through popular daily deals website, Groupon, had their names, emails and voucher details distributed by accident on Saturday.
The information was shared amongst everyone who bought a voucher, thought to be more than 1000 people.
With the information out, Fairfax Media, who first uncovered the story, said that some customers then found themselves in a situation where others had used their vouchers before they could.
The breach was discovered on Saturday morning and customers received a email that evening informing all vouchers had been cancelled. The total cost of vouchers was $1,308,505 and customers have since be given new gift cards.
Data shared amongst customers came in the form of a spreadsheet instead of a PDF copy of their expected voucher.
Visitors to the Groupon site originally purchased $100 or $200 vouchers sold to them at a 7.5 per cent discount.
Woolworths has not released anything about how the data breach occurred. The supermarket has however said that it takes customer data breaches seriously and that they are working to resolve the technical problem.
