Apple on Monday released iTunes 12.2.1, fixing a critical problem that would cause tracks matched via iTunes Match to be converted to Apple Music content instead.
The issue was a potentially serious one, since tracks linked with Apple Music have copy protection, and are no longer playable if a subscription to that service expires. Tracks uploaded to iTunes Match are owned by the person in question and are supposed to be freely copyable when downloaded to a device.
Mac owners can fetch the update through the Updates tab at the Mac App Store. Windows owners should be able to grab the software shortly via the Apple Software Update tool, or else via direct download.
Still unresolved is a problem with iCloud Music Library -- which links iTunes Match and Apple Music -- that can substitute bad metadata and artwork, generate duplicates, or even wipe out entire playlists and the music within them. Numerous people have complained on Apple's support forums, although there do appear to be ways of recovering library data such as using old ITL files or restoring from backup, depending on the severity of the damage.