Hi Jared,
This is more of a browser issue in handling filetypes filter. In this case Firefox fails to filter these string extension: bmp,csv,doc,gif,ico,jpg,jpeg,odg,odp,ods,odt,pdf,png,ppt,swf,txt,xcf,xls,BMP,CSV,DOC,GIF,ICO,JPG,JPEG,ODG,ODP,ODS,ODT,PDF,PNG,PPT,SWF,TXT,XCF,XLS.
However it works for simple one like jpg,png,gif for example. But the important part is that it is blocked by Javascript so that the files won't make into upload queue thus it would not be uploaded anyway. See screenshot below:
stackoverflow.com/questions/10802681/how...ploads-html5-runtime
http://moxiecode/plupload#1050