1388677 - Firefox sometimes add .xls to .xml file when downloading with the correct mimetype

Status: NEW

(Firefox :: File Handling, defect, P3)

Description

[mathieunachury]

User Agent: Mozilla/5.0 (Windows NT 6.1; rv:54.0) Gecko/20100101 Firefox/54.0
Build ID: 20170628075643

Steps to reproduce:

I tried to download(Open) a OpenXml Excel spreadsheet using the mimetype : "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet".

/!\ This bug seems to appear only after a similar mimetype file has been downloaded(save)/!\

After a download(Save) this lines:
"<RDF:Description RDF:about="urn:mimetype:application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                   NC:value="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                   NC:fileExtensions="xlsx">
    <NC:handlerProp RDF:resource="urn:mimetype:handler:application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"/>
</RDF:Description>
"
are added on the "mimeTypes.rdf" file inside my appdata/roaming/.../profile.
Before that the download(open) works file.

Doing a Download(save) never add any extention to the file.

Deleting the "mimeTypes.rdf" file fix the issue until a re-download(save) is performed, that then re-add the lines.

I have checked that I have the default mimetypes for all Office and xml extension in my registry.


Actual results:

Firefox propose me to open it using Microsoft Excel and does it.
But it add an .xlsx extention to the file. (.xml.xlsx).
The file is then non-openable by Excel.


Expected results:

Firefox propose me to open it using Microsoft Excel and does it.
(Without modifying the file extention)