JFIF file seems to have unsupported meta data that is disliked by ImageIO.

This causes it to generate funny Mime Type.

You can test this image using this wiki markup:

!genuine-engraved logo on side cover.jpg|thumbnail!

Need to have a better error message that informs users about this, current error message only says:

Could not generate thumbnail: Image file format not supported

Perhaps we should say Confluence was unable to retrieve meta data from the JPEG file. Either this or we update the documentation saying that we only support EXIF standard.