I wanted to upload and link to a .patch file in one of my wiki pages, but the upload facility wouldn't let me: Permitted file types: png, gif, jpg, jpeg, doc, xls, mpp, ods, odt, pdf, ppt, tiff, bmp, docx, xlsx, mov, pptx, ps. So I renamed the patch file to have a .doc extension, but then got a warning that I couldn't upload a .doc file because Internet Explorer doesn't like it: Cannot upload this file because Internet Explorer would detect it as "application/msword", which is a disallowed and potentially dangerous file type. This despite the fact that .doc is listed as a valid extension above. In the end I had to rename my .patch file as a .docx, then write a note to the user that it wasn't actually a .docx file. Also, the 'Ignore any warnings' checkbox apparently doesn't do anything since checking it didn't ignore those warnings.
I have configured the wiki to allow the file types requested. The "application/msword" MIME type is currently blacklisted because it could be used to spread malicious code. This will be addressed in an update to Mediawiki.