Under Armour Inc., joining a growing list of corporate victims of hacker attacks, said about 150 million user accounts tied to its MyFitnessPal nutrition-tracking app were breached earlier this year.

An unauthorized party stole data from the accounts in late February, Under Armour said on Thursday. It became aware of the breach earlier this week and took steps to alert users about the incident, the company said.

Shares of Under Armour fell as much as 4.6 percent to $15.59 in late trading following the announcement. The stock had been up 13 percent this year through Thursday’s close.

The data didn’t include payment-card information or government-issued identifiers, including Social Security numbers and driver’s license numbers. Still, user names, email addresses and password data were taken. And the sheer scope of the attack — affecting a user base that’s bigger than the population of Japan — would make it one of the larger breaches on record.

Source: Under Armour Data Breach: 150 Million MyFitnessPal Accounts Hacked | Fortune