I just downloaded a zip file and extracted it using Windows 7's built-in zip extraction (right-click on zip file --> "Extract All..."). Somehow it resulted in folders that are automatically encrypted - i.e. green folder name in Windows Explorer, and if you open "Properties" --> "Advanced...", you see the "Encrypt contents to secure data" checkbox is checked.
What would be the cause? I have tried extracting other zip files, still using Windows 7's built-in zip extraction, and I don't get encrypted output.
I have also tried extracting the same zip file using 7-zip 9.20 64-bit, on the same Windows computer, and I don't get encrypted output.
To be exact, I am talking about the Mercedes-Benz Mixed Tape Compilation #58 zip file, available at http://dl.mixedtape.mercedes-benz.com/latest/Mercedes-Benz_Mixed_Tape.zip (the link is time-dependent, as Mercedes-Benz reuses the same URL for each compilation zip file, so it will be valid only for the next 10 weeks or so; after that, the same URL will probably serve compilation #59 when that comes out). If you can't download that directly, you may need to go through their website first: http://mb.mercedes-benz.com/en/mixedtape/