Affects both the desktop and online Office suite. What telemetry data was collected isn't documented and can't be opted out of. Microsoft is said to be already working on addressing these issues to avoid a huge fine.Investigators […] found that Office applications also collected actual content from users' applications, such as email subject lines and sentences from documents where the company's translation or spellchecker tools were used.
For me, telemetry should be off by default and (seeing as this is a commercial product) one should be paid or otherwise compensated for participating in a user study.