I have been trying Ext.exporter.File with regular files and images and it does not work as expected.
It always generates files as UTF-8 BOM. Tested the same with the latest https://github.com/eligrey/FileSaver.js and is working OK.
Can you please update your internal implementation. I know we can just use NPM and use it directly, but since it's implemented on ExtJS it would be nice to have it working as it should.
Also, I know it's easy, but you could also add saveBase64As(...)
Thanks