Reporting across 100+ sites, I've seen others reporting this as well. Appears to be MS update related, disposition changed and is now flagging as malicious/blocked. 1000's were allowed through before disposition was changed. Same thing happened about a year ago, related to an MS update.
Source: 9.tlu.dl.delivery.mp.microsoft.com
[http://9.tlu.dl.delivery.mp.microsoft.com/filestreamingservice/files/8dea8123-fd8f-492c-9c2d-7cdfab740447?P1=1681398256&P2=404&P3=2&P4=MfVNhcdbZfud6jewyT%2b8ana%2b8c9bZAGjTJzFleDabV567nUloqLAlJM78V5wGwfOSpnIKNtbXOKduQ%2fJeWBylQ%3d%3d]
