[whatwg] overriding MIME type in accept attribute?

[Hallvord Reiar Michaelsen Steen]

This part of the WF2 spec about the file upload: "accept" attribute 
seems a bit odd to me:

> UAs may allow the user to override the MIME type to be one of the 
> allowable types if the file is originally incorrectly labeled (but 
> should not allow users to override the type merely to let 
> submission continue, as that would defeat the point of having a 
> restriction in the first place)

How is the UA to allow the user to override a MIME type and how on 
earth is it supposed to know the user's motivation for doing so?

Another issue: on Windows, if I try to upload a file with no 
extension, how is the UA supposed to work out what the MIME type is? 
Content sniffing?

-- 
HRMS