On the topic of backups, 7zip recently changed its handling of the FILE_ATTRIBUTE_ARCHIVE bit on unzipped files which caused an issue with some old software I was using. This is from the old DOS days with the BACKUP/RESTORE commands - the bit was set if any backup was made of the file. It's comically naive because it only assumes a single backup and this bit was forgotten to the sands of time until it was disturbed by some meddling kids!