The filename in Content-Disposition header is currently generated as UTF-8, which leads to bugs such as EXPLORER-177 (a russian filename being seen by the browser as "_038AB@0BC@0 >AA8O 8 AB@0=K &5=B@.8 _>AB._2@>?K.pdf").
We may follow the RFC 6266 recommandation, which is implemented by most browsers, and add a UTF-8 encoded "filename*" header.