Agreed it is semantics... However, The data was stolen, it doesn't matter how many hands it passes through it remains stolen data not leaked data. Leaked has connotations of accidental or minor. The word stolen more accurately represents the truth here.
Leaked data to me infers that it was someone inside the organisation who released data by accident or deliberately but covertly. Such as government leaks etc.
I am angry about what these criminals have done and the word stolen carries more weight than leaked. Using leaked seems to take some of the impact away. For example which of the following more accurately relays your anger over the current situation?
AJ Online Services used leaked data to send emails to.....
AJ Online Services used stolen data to send email to.....
Just my opinion tho