Update checker is ignoring the http proxy
I was using the Mullvad Browser configured to use HTTP proxy to a network that does not have internet-facing exits, a secure isolated LAN kindof.
Then the Mullvad Browser notified me that there are updates available.
This means that the code that checks for updates are not using the proxy configuration, but checks for updates out-of-band. (Remember, the network I had connected to does not allow for connections to the internet.)
This is a privacy risk, as it identifies a user as using the Mullvad Browser. It should OF COURSE use the configured proxy for obtaining the information that there is a new version out..!?
I have not tried replicating it, but I have found the following blog post which might or might not be relevant: https://blog.mozilla.org/security/2021/10/25/securing-the-proxy-api-for-firefox-add-ons/ & https://ftp.mozilla.org/pub/system-addons/proxy-failover/