> This isn't any different from many download procedures. Consider that even a general-purpose package manager like Pacman uses HTTP, because there's little point in using transport-level security when the payload is cryptographically signed and there's a solid root of trust.
This IS different.
If the VLC update is signed with a key not known to VLC, VLC will then go fetch the new key from the update server over HTTP, and not verify the key in any other way.
This renders the cryptographic signing of the updated binary a complete no-op. Anybody in a position to tamper with the HTTP download of the signed binary can equally change the HTTP downloaded, unverified key VLC retrieves to verify the signing. It is effectively unsigned, and the root of trust is as solid as mist.