Under Armour has reported that data from some 150 million MyFitnessPal diet and fitness app accounts was compromised last month, in one of the biggest hacks in history. As a result of the massive hack, Under Armour shares dropped down 3% in after-hours trade, according to Reuters.

In a statement released by Under Armour, the company revealed that the stolen data includes account user names, email addresses and scrambled passwords for the popular MyFitnessPal mobile app and website. However, much more important information, such as Social Security numbers, driver license numbers and payment card data were not compromised.

"Four days after learning of the issue, the company began notifying the MyFitnessPal community via email and through in-app messaging," the official company statement reads. "The notice contains recommendations for MyFitnessPal users regarding account security steps they can take to help protect their information. The company will be requiring MyFitnessPal users to change their passwords and is urging users to do so immediately."

Under Armour says it is working with data security firms and law enforcement, but they did not provide any details regarding how the hackers got into its network or pulled out the data without getting caught in the act.

The hack is reportedly the largest data breach this year and one of the top five to date, according to SecurityScorecard. Reuters reports that larger hacks include the 3 billion Yahoo accounts compromised in a 2013 incident and credentials for more than 412 million users of adult websites run by California-based FriendFinder Networks Inc in 2016.