The grocery chain Tesco saw thousands of its customers emails and passwords posted online. And customers have complained that their vouchers have gone missing from their accounts.

Many of the customers took to Tesco's Facebook page to post complaints that they were booted out of their accounts and that their points and vouchers were stolen.

The grocery chain said that it was "urgently investigating" the situation.

"We have contacted all customers who may have been affected and are committed to ensuring that none of them miss out as a result of this," Tesco said in a statement.

"We will issue replacement vouchers to the very small number who are affected."

Trey Ford, global security strategist at Rapid7, said: "The attackers seem to have picked up usernames and passwords that were leaked after breaches of other, potentially unrelated organizations, and by trying them on Tesco’s site, they were able to compromise 2,239 Tesco.com customer accounts."

"So far the information available indicates that the impact of this has been relatively limited – stolen vouchers – but if attackers have tried this on Tesco.com, the chances are they are also trying it on other sites too and so we may see additional fallout."



It is thought that the hack was a result of other sites being hacked and then tried out on Tesco.com by the hackers.