Today, Apple issues an update for MacBook Pro systems:

“MacBook Pro Flash Storage Firmware Update 1.0

This update is recommended for MacBook Pro (mid 2015) models. This update addresses a storage firmware issue that, in rare cases, may cause data corruption.”

I don’t know any more details of any security fixes…

https://support.apple.com/kb/DL1830?locale=en_US
https://support.apple.com/downloads/DL1830/en_US/macbookproflashstoragefwupd1.0.dmg