Any requests to domains marked to open in a container are turned into GET requests

[cyang1]

• Multi-Account Containers Version: 6.1.1
• Operating System + Version: macOS 10.14.6
• Firefox Version: 70.0.1
• Other installed Add-ons + Version + Enabled/Disabled-Status:

  Amazon.com  1.1 true    amazondotcom@search.mozilla.org
  Bing    1.0 true    bing@search.mozilla.org
  DuckDuckGo  1.0 true    ddg@search.mozilla.org
  eBay    1.0 true    ebay@search.mozilla.org
  Firefox Multi-Account Containers    6.1.1   true    @testpilot-containers
  Google  1.0 true    google@search.mozilla.org
  Imagus  0.9.8.72    true    {00000f2a-7cde-4f20-83ed-434fcb420d71}
  Livemarks   2.4 true    {c5867acc-54c9-4074-9574-04d8818d53e8}
  Reddit Enhancement Suite    5.18.7  true    jid1-xUfzOsOFlzSOXg@jetpack
  Tampermonkey    4.9.5941    true    firefox@tampermonkey.net
  Twitter 1.0 true    twitter@search.mozilla.org
  uBlock Origin   1.23.0  true    uBlock0@raymondhill.net
  Wikipedia (en)  1.0 true    wikipedia@search.mozilla.org

Actual behavior

When making any request from outside a container to a domain that is marked to open in a specific container, requests of any type are always turned into a GET request, losing any payload in the process.

Expected behavior

The request method and payload (and probably other request metadata as well) are preserved when making requests across container boundaries.

Steps to reproduce

This is just using posthere.io as an example to inspect the resulting request created, any page that allows you to see what method was used in the request will work.

1. Navigate to posthere.io, mark it to open in a specific container (like Work for example)
2. Create a page with a <form action="https://posthere.io/your-token-here" method="POST">, and open it outside of any container.
3. Submit the form and note that the request was turned into a GET request.

Notes

Concretely, this breaks features of certain apps, like the Dropbox desktop client's "View on Dropbox.com" context menu option, which relies on making a POST request from a local file:// to a dropbox.com endpoint to sign in and redirect.

[Farow]

Another example: if you make a search on searx.me and then re-open it in a different container, you will lose the search query.

It seems like there's no direct api to open a new tab/container with an http post request. However, there seems to be a workaround by opening an internal redirect page which will make the proper request instead: https://stackoverflow.com/a/23687543

[pawca]

Hi.

What is the state on this issue?

Also wondering, is this issue a

1. bug in the multi account container plugin
2. bug in firefox
3. a feature (wanted limitation) in firefox

What needs to be done to fix this quite annoying problem?

Thank you very much.

PS: i'm using the plugin together with searx.

[pawca]

Hello again.

Unfortunately this bug is really annoying. But no more response in more than 2 months. Am I the only who cares about this? Any feedback and response is very much welcome.

Thank you for your efforts!