Over 2,000 customers of Tesco - the U.K.'s biggest supermarket - have had their personal details posted online after a data breach at the company by computer hackers.
Tesco has now deactivated some customers' net accounts after login names and passwords were shared online on a popular text-sharing website, according to a report by the BBC.
Hackers used data stolen in other high-profile security breaches to draw up the list of Tesco.com details and found that more than 2,000 customers had used the same email and password combinations on the other sites, according to the reports.
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Tesco told CNBC that it takes the security of its customers' data extremely seriously and is urgently investigating these claims.
"We are contacting all customers who may have been affected and are committed to ensuring that none of them miss out as a result of this. We will issue replacement vouchers to the very small number who are affected," a spokesperson said in an e-mailed statement on Friday morning.