Files names containing special characters get garbled during the file processing.
- "štěně.png" => "Å¡tÄnÄ.png"
This is caused by a specification conflict:
By XHR2 specification FormData is encoded as utf8 and the charset of the XHR isn't specified (since it cannot be changed).
On server side the request parser looks for the charset and when it doesn't find it uses the default, which by HTTP/1.1 specification is iso-8859-1.
(The default can apparently be changed in Tomcat but not in WildFly)