1554345 - Developer Tools show original response headers, without modifications by extensions

Status: NEW

(DevTools :: Netmonitor, defect, P3)

Description

[jscher2000]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:67.0) Gecko/20100101 Firefox/67.0

Steps to reproduce:

Install my extension https://addons.mozilla.org/firefox/addon/content-type-fixer/

Load my test page https://www.jeffersonscher.com/res/badct/

Open Network Monitor and Browser Console

Then try the first or second link on the page (returns zip file).

Actual results:

Network Monitor main display shows the Content-Type value was correctly overridden to application/pdf

Headers panel for the request shows the original Content-Type header value of text/plain

The headers shown in the Browser Console or Web Console similarly show the original Content-Type header value of text/plain

Expected results:

It would be more helpful if the headers showed the values after modifications by extensions. This could be a change from earlier versions, but I have not run a mozregression.

Comment 1

[jscher2000]

Firefox 60.7.0esr (Portable Edition) is the same, so probably not a regression.

(mozregression was difficult to test with extensions due to Armagadd-on 2.0, so I gave up on that)

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The priority flag is not set for this bug.
:Honza, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 3

[Teun van Eijsden]

Is it true that there is no way to view the actual/effective headers (in my case a CSP header that is changed by multiple extensions) in the DevTools?
I don't understand @jscher2000's comment:

Network Monitor main display shows the Content-Type value was correctly overridden to application/pdf

in my Developer Tools > Network tab, the original HTTP headers from the server are shown, not the "correctly overridden" ones.

Comment 5

[u669213]

You can see response headers including those modified by extension in about:cache?storage=disk
For example if you open this url http://textfiles.com/images/textfile.gif
You can see here both original and after modifying by extension response headers: about:cache-entry?storage=disk&context=&eid=&uri=http://textfiles.com/images/textfile.gif

Since it gets cached you have to click refresh while holding shift key to avoid cache after modifying by extension that example url.

Example rule I used in extension Header Editor:
name: textfiles
rule type: Modify response header
match type: URL
match rules: http://textfiles.com/images/textfile.gif
Execute type: normal
header name: last-modified
header value: Wed, 10 Nov 2020 03:46:28 GMT

Now this is shown in about:cache-entry?storage=disk&context=&eid=&uri=http://textfiles.com/images/textfile.gif

original-response-headers: Date: Mon, 05 Jul 2021 11:02:35 GMT
Server: Apache/2.4.37 (FreeBSD) OpenSSL/1.0.2o-freebsd
Last-Modified: Wed, 10 Nov 1999 03:46:28 GMT
ETag: "e7f-358ee5560cd00"
Accept-Ranges: bytes
Content-Length: 3711
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: image/gif

response-head: HTTP/1.1 200 OK
Date: Mon, 05 Jul 2021 11:02:35 GMT
Server: Apache/2.4.37 (FreeBSD) OpenSSL/1.0.2o-freebsd
ETag: "e7f-358ee5560cd00"
Accept-Ranges: bytes
Content-Length: 3711
Content-Type: image/gif
Last-Modified: Wed, 10 Nov 2020 03:46:28 GMT

Notice the difference in last-modified. Of course in network monitor only original are displayed.