Sports apparel maker Under Armour Inc. revealed Thursday that its MyFitnessPal service had been hacked with the account details of 150 million users being stolen.

MyFitnessPal is a smartphone app and website offered by the company that tracks diet and exercise to determine optimal caloric intake and nutrients for the users’ goals, using gamification elements to motivate users.

How the hack took place was not disclosed. Under Armour said in a statement only that “an unauthorized party acquired data associated with MyFitnessPal user accounts in late February 2018” and that it immediately moved to shut down the data breach.

Account data stolen is said to include usernames, email addresses and “hashed” or scrambled passwords. The majority of passwords were hashed by bcrypt, an encryption standard that is more difficult to crack than other forms of encryption but not impossible.

The data stolen did not include government-issued identifiers such as Social Security numbers and driver’s license numbers, since Under Armour said it doesn’t collect those details from users. Credit card information is said to have been stored on a different server and wasn’t affected.

“While there aren’t many details yet, as with most breaches, it points to a lack of proper security hygiene, specifically around protecting user data,” Mike Kail, chief technology officer at CYBRIC Inc., told SiliconANGLE.

Despite Under Armour saying it contacted affected users, Kail noted that his wife, who uses the app, has not. That, he said, suggests that “it’s likely Under Armour does not yet have a precise handle on the severity of the situation,” and he expects more information to emerge over the next 24 hours.

“Unfortunately, until we see organizations adopt a more proactive approach to security, including establishing a process for continuously monitoring which applications might have vulnerabilities, we’ll continue to be made aware of similar instances,” Kail added.

News of the hack drove Under Armour’s stock price down. CNBC reported that it dropped as much as 3.8 percent before recovering slightly Thursday.

Image: Under Armour