This is a program that utilizes FSRM for Windows Server privileges. Initially he could only do arbitrary file deletions, but now he can do arbitrary file writes.
MSRC response: 
And it's not the default service, so I'm publicizing it and discussing the case with the community.
You need to create a file expiration task first.
The scope is set to C:\test. the expiration directory is a random directory.
And set the expiration condition to be a file name matching *.txt ( actually makes it harder to exploit ).