Files with sage file suffix can be notoriously encountered on computers affected by the Sage ransomware.
SAGE file extension - Sage ransomware affected data
What is sage file? How to open sage files?
File type specification:
The sage file extension appears to be since January 2017 used by one of the ransomware types, this one labeled as Sage.
It is mainly distributed via scam emails that contain no subject, but a .zip file in the attachment.
Every affected folder will also contain a ransom note saved as !Recovery_[3_random_chars].html file.