Millions of Dixons Carphone customers have had their financial and personal data illegally accessed after a major breach at the United Kingdom company.
The compromised data didn't include PIN codes, CVV numbers, or any other personal or authenticating information that could lead to fraudulent use.
The successful hack saw "an attempt to compromise" 5.8 million credit and debit cards, but only 105,000 cards that lacked chip-and-pin protection were leaked, the company said.
It admitted non-financial personal data, such as name, address or email address, was accessed but it again insisted that it had seen no evidence of any fraud at this stage.
The company's shares lost 5% of their value when trading began on Wednesday morning shortly after the disclosure.
"We are extremely disappointed and sorry for any upset this may cause", said Chief Executive Alex Baldock.
'The protection of our data has to be at the heart of our business, and we've fallen short here.
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Dixons Carphone said it had immediately notified the relevant card companies so that they could protect customers.
Yesterday also saw Yahoo's United Kingdom arm fined £250,000 for a data breach in 2014 which affected more than 500 million users.
However, an additional 105,000 cards from outside the European Union - with no chip-and-pin protection - have been compromised as part of the breach.
Because the data breach dates back to past year it will be dealt with by the ICO under the powers of the Data Protection Act 1998 and not the European Union General Data Protection Regulation (GDPR) which went into effect on May 25.
The company has launched an investigation into the incident and is said to be engaged with cyber security experts.
Last month Dixons Carphone warned on profits and said it would have to close shops, wiping more than 500 million pounds off its market value.
They claim stolen data is not believed to have left internal systems, but are advising customers to take protective steps anyway.
According to a statement made by the company, the security breach was discovered during a recent review of the company's systems and data.