The website of the UK's largest grocer went offline over the weekend after being hacked.
It is currently not believed that any customer information was stolen, but users were unable to place or amend orders at British retailer Tesco from early Saturday to late Sunday.
“An attempt was made to interfere with our systems which has caused problems with the search function on the site," Tesco said in a statement.
"We’re working hard to fully restore all services and apologize for the inconvenience… There is no reason to believe that this issue impacts customer data and we continue to take ongoing action to make sure all data stays safe.”
The outage proved particularly annoying for some due to a quirk in the way Tesco allows people to order grocery deliveries.
With a limited number of delivery slots on its website, users often quickly file dummy orders for the same item multiple times to secure a delivery. They then update the order closer to the delivery time.
This was not possible with the outage, so customers reported receiving orders featuring dozens of the same item. “I need to edit my shop for tomorrow (currently all it is is a banana) I always edit the shop the day before," one shopper tweeted.
Another told the BBC: "We were meant to get a week's shop this morning. The website was down all yesterday so we couldn't amend or cancel. All we received was 120 cans of Pepsi Max."
Shoppers criticized the lack of communication during the outage, and the inability to cancel orders over the phone.
While services have returned, Tesco said that people may have to be put into a waitlist due to the increase in traffic.
Back in 2014, the data of more than 2,000 Tesco shoppers was posted online. Two years later, hackers stole £2.3m from Tesco Bank customers.