Uploading files to direct to S3 from another site using CORS failes if HTTPS Everywhere is installed
Version: 3.4.2 on Firefox 25
Many sites have a file upload feature that uses AWS S3's ability upload files directly to S3 using CORS. There is a jquery library that makes this easy.
http://blueimp.github.io/jQuery-File-Upload/
If HTTPS everywhere is installed on Firefox 25 the OPTION request is never made. If HTTPS Everywhere is disabled and firefox is restarted the upload will work.
Trac:
Username: myers
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information