It sounds like you have to manually copy files from the plugins website to your own website. If it's in production, I suppose you're not going to enable or disable the plugin often (as you would in development), so this will be a one-time process.
In addition, by doing so in this way, your personal assets are saved from public folders, maintaining the security you are worried about.
On the other hand
If the plugin is open source, make a simple exit and discard the entire suction cup in the web root. If this is compromised, you do not care, because the files are freely distributed in any case.
source share