Affected versions

• Firefox 72.0a1 (BuildId:20191126212708)

Affected platforms

• Windows 10 64bit.
• Ubuntu 18.04 64bit.
• macOS 10.13

Preconditions

• Create a wireless hotspot via Windows 10
• Go to the Registry Editor Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters and add several ICS domains
• Connect the test device to the hotspot.

Steps to reproduce

1. Launch Firefox.
2. Access the about:config page
3. Set the network.trr.mode pref to 2
4. Access the about:networking#dns page

Expected result

• The ICS domains are parsed inside the about:networking#dns page under the Suffix List

Actual result

• Windows ->

1. It seems that if there is only 1 ICS domain, it parses that domain successfully but the domain is still being handled via TRR
2. It seems that if there are multiple ICS domains (separated by comma) they are parsed as one (See the attached screenshot).

• Ubuntu

1. It seems that if there are multiple ICS domains they are not being parsed at all inside the about:networking#dns page. If there is only one ICS domain it gets successfully parsed inside the about:networking#dns page.
2. The domain request is being handled via TRR

• macOS

1. It seems that macOS platforms are not parsing ICS domains at all

• Android

1. Android platforms seems to successfully parse the ICS domains (even if there are multiple domains) and the domain requests are not being handled via TRR

Downgrading priority since ICS is not a very common use case.