Tesco was hit by a cyber attack on February 13th that resulted is over 2,000 customer email addresses and passwords being posted online.
The criminals used the details to steal Tesco vouchers from shoppers, reports the BBC.
Tesco has said in a statement that its has contacted all customers who may have been affected and are ‘committed to ensuring that none of them miss out’ as a result of the cyber attack.
The grocer will issue replacement vouchers to those affected.
This is not the first time Tesco has been targeted by cyber criminals. Last year hundreds of owners of Tesco Clubcards reported their loyalty card accounts has been hacked.