Investigate warning about Uncloak canonical name uBlock Origin setting

[ruihildt]

Enabling Uncloak canonical names in uBO will create a "mild" DNS leak: the Mullvad VPN server you're connected to will appear when connecting through proxy.

This is because webextension are not aware of each other, so uBO will not "know" every connection should be proxied, and when uBO will try to resolve a domain to check if this is in fact a tracking one, this will be done outside of the proxy but still inside of the Mullvad VPN tunnel.

To avoid this leak, and unless Firefox fixes the reported bug, the only option is to disable this uBO option.

While extensions are not aware of each other, with the correct permission, it is possible to list installed extensions. This is how we can recommend uBO when not installed.

So a possibility would be to recommend disabling Uncloak canonical names when a proxy is in use.
Unfortunately, it will not be possible to check whether the option is enabled or disabled, so it would need to be a "passive" recommendation the user should be able to dismiss.