On March 25, 2018, Under Armour became aware that during the month February of this year an unauthorized party acquired data associated with MyFitnessPal user accounts
A post on the MyFitnessPal site shares the details known so far and offers some guidance for affected users. It explains that Under Armour is notifying all MyFitnessPal users to provide information about how to protect their data, requiring all users to change their passwords, working with law enforcement to investigate and continuing to monitor for suspicious activity, and exploring enhancements to help detect and prevent similar unauthorized access in the future.
The details about how Under Armour was breached are not available yet. The information that Under Armour knows was accessed: