I’m currently writing an application that uses XSLT to change the output style of the data from XML to JSON and I needed the .xslt file hosted somewhere. Because I’m feeling lazy right now I figured I’d just upload the .xslt file to my WordPress blog and point my code there. I got the following error when I tried to upload it in the WordPress Media library:

Sorry, this file type is not permitted for security reasons.

If you have access to your WordPress application files, you can edit functions.php in /wordpress/wp-includes to allow the file extension. In my case I added this line in the get_allowed_mime_types() function:

'xml|xsl|xslt' => 'text/xml',