That is not really auto-update (only if you enabled it system-wide) – and after reviewing the source code, which is necessary anyhow to make sure it is actually

That is not really auto-update (only if you enabled it system-wide) – and after reviewing the source code, which is necessary anyhow to make sure it is actually ‘secure’, you would then remove the file in /etc/apt/sources.list.d and be happy :-)