The Marks & Spencer website had to be taken down temporarily on Tuesday after some customers said they saw other people’s private details when they logged into the site.
Marks & Spencer said the security breach was due to a technical glitch and that there had been no third party attacks.
Customers’ full credit card details were not leaked, the company said. However it was unable to confirm how many customers had been affected.
Personal details such as names, dates of birth, contacts, and previous orders were leaked.
A spokesperson said the website was suspended between 6.30pm and 9pm while the breach was investigated.
"This allowed us to thoroughly investigate and resolve the issue and quickly restore service for our customers. We apologise to customers for any inconvenience caused,” the spokesperson said.
The British telecoms company TalkTalk also suffered a major security breach in October due to a DDoS cyber attack.
