Containered JS windows are moved to a tab

[bllngr]

• Is "Firefox will: Never remember history" in the Firefox Preferences/Options under "Privacy & Security > History" selected? Yes/No: No
• Are you using Firefox in a Private Window? Yes/No: No
• Can you see a grayed out but ticked Checkbox with the description "Enable Container Tabs" in the Firefox Preferences/Options under "Tabs"? Yes/No: Yes
• Multi-Account Containers Version: 6.0.0
• Operating System + Version: Windows 10
• Firefox Version: 59.0.2 (32-bit)
• Other installed Add-ons + Version + Enabled/Disabled-Status: Awesome RSS 1.2.4 true {97d566da-42c5-4ef4-a03b-5a2e5f7cbcb2} Chrome Store Foxified 3.4 true Chrome-Store-Foxified@jetpack ColumnCopy 0.5.0 true lapbbfoohlcmlbdaakldmmallcbcbpjb@chrome-store-foxified-811806531 Cookie AutoDelete 2.1.2 true [email protected] Distill Web Monitor 1.10.3 true {7a73dc4b-1b38-40e7-ac56-7d356dd4af34} Firefox Multi-Account Containers 6.0.0 true @testpilot-containers Hover Zoom+ 1.0.127 true {1f50c5bd-711d-441f-8cdf-d2043bcce0f9} HTTPS Everywhere 2018.4.11 true [email protected] Pushbullet 335 true jid1-BYcQOfYfmBMd9A@jetpack Stylish - Custom themes for any website 3.0.4 true {46551EC9-40F0-4e47-8E18-8E5CF550CFB8} Tab Auto Refresh 0.1.3 true {7fee47a1-8299-4576-90bf-5fd88d756926} uBlock Origin 1.16.0 true [email protected]

Actual behavior

Opening containered pages via window.open(...) opens them in a window, and then moves them into a tab immediately.

Expected behavior

They should open and stay in a window.

Steps to reproduce

1. Set e.g. https://mozilla.org to always open in a container
2. Create a bookmarklet with the following address: javascript:(function(){window.open("https://mozilla.org",%20"_blank","height=900,width=900,location=no,menubar=no,location=no,toolbar=no,left=100,top=100");})();
3. Click on it, and observe the window.