Online Retailer Coupang Owns Up to Big Blunder. The Stock Drops.

Coupang is a dominant online retailer in South Korea. (SeongJoon Cho/Bloomberg)

Key Points

• Coupang’s stock fell 4.4% in premarket trading after the online retailer said a data breach had affected 33.7 million customers.
• The breach, occurring from June until recently, exposed names, email addresses, phone numbers, and order information.
• The online retailer’s stock had gained 28% this year through Friday’s close.

The South Korean online retailer Coupang has been having a pretty good year, but that looks set to change after a huge data leak sent its U.S.-listed stock lower.

Coupang stock was down 4.4% in premarket trading in New York, after the company apologized over the breach, which affected 33.7 million customer accounts.

“We sincerely apologize for any inconvenience and concern caused to our customers,” Coupang CEO Park Dae-jun posted on the company’s website on Sunday, in a statement translated by Barron’s using online tools.

Someone gained unauthorized access to customer information from June of this year up until recently, including names, email addresses, phone numbers, and certain order information, according to the company. However, login details and payment information weren’t breached.

Coupang said it would cooperate with Korean authorities. Local media reported that a former employee from China was suspected of being behind the breach.

“On November 18th, Coupang became aware of unauthorized personal data access involving about 4,500 customer accounts. Coupang immediately reported the incident to relevant authorities…Subsequent investigation has revealed that the extent of customer account exposure is about 33.7 million accounts, all in Korea,” a company spokesperson said in an emailed statement.

“According to the investigation so far, it is believed that unauthorized access to personal information began on June 24, 2025, via overseas servers,” the spokesperson said.

The leak is an embarrassment for the company, which is headquartered in the U.S. but does the vast majority of its business in South Korea. Its dominance in e-commerce there is often compared with Amazon.com’s position in other markets. The stock had gained 28% this year so far through to Friday’s close.

Write to Adam Clark at adam.clark@barrons.com