You most likely will NOT get much of an an official answer from WD other than what they post in firmware readme/change log file and what one of their staff has posted previously (see this link for example).
For the single bay My Cloud units (know you mentioned you have a Mirror) there were two separate discussions on the various security issues with the single bay/drive firmware.
http://community.wd.com/t/endgadet-warns-about-security-problem/198086
http://community.wd.com/t/latest-firmware-still-vulnerable/96743
Short answer, no one knows for certain until the various My Cloud units updated firmware is tested against the various (and many) exploits previously publicly announced.
