Apple has begun pushing a small firmware update to the 2015 MacBook Pro, bringing a fix for an issue with the flash storage that could potentially result in data corruption.
Here's how Apple describes the fix:
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.
The update is pretty small, clocking in at just 1.9MB, and should be available for 2015 MacBook Pro owners from the Mac App Store, or as a direct download from Apple at the link below.