1981797 - Firefox does not recognize/sniff docx files sent with text/plain mimetype as download

Status: NEW

(Core :: Networking: HTTP, defect, P2)

Description

[Melissa]

Attachment: Screen Shot.jpg

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:141.0) Gecko/20100101 Firefox/141.0

Steps to reproduce:

I am trying to download a docx file. I have tried to open it, I have tried to save it. I have installed all updates to Windows, Mozilla, and Word. I still have this issue. This issue is new because I have downloaded these files before. I can download in Google Chrome so it is not the website. Apparently this issue has happened before but there doesn't seem to be a resolve. I don't know how to roll back an update.
https://bugzilla.mozilla.org/show_bug.cgi?id=1610439

Actual results:

I get gargally goop text that can't be read. There is not a popup that allows me to save even though it is marked save as or ask to save in my settings.

Expected results:

Open Word document (Docx) or Saved Word document.

Comment 1

[BugBot [:suhaib / :marco]]

The Bugbug bot thinks this bug should belong to the 'Toolkit::Application Update' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[:Gijs (he/him)]

I added the URL from the screenshot in comment 0 to the URL field of the bug. I can reproduce the problem outlined in comment 0 - the server tells the browser that this is a text/plain document (in the Content-Type header). This is wrong. However, it seems that Chrome also gets told the file is text/plain but does manage to start a download. So I assume that there is some kind of sniffing that ought to happen here but isn't. Over to the networking team to have a look at this.