Although .nef files are actually images created by the Nikon D70, MediaWiki considers them as possibly malicious. See https://commonsarchive.wmflabs.org/wiki/File:20050525-033-lido.nef for example.
Commons should not be here. And also, triaged as Low priority because this is not much of an issue, although it would be better if the misleading warning is removed.
I do not see such a warning on that page, nor anything similar. Can you make a screenshot and point it out to me?
Oh, you're right, there was no warning. My mistake. :)