As far as I’m aware, most of the “dangerous” lua api (io/network etc) is blocked and only available to mods during the startup phase, and not otherwise during runtime.
But I’m sure there are workarounds. For one, I’ve written mods with rust for it, and you can require and then call any dynamic library through lua, with all of the io and networking you’d want, as long as it is brought in during the init phase. And the mods that do access the “dangerous” api, have to be explicitly given rights to do so (but again, by the server, not the clients) in the config before it works.
It’s not that bad for the most cases, as long as you trust the server. If playing single player, you personally control which mods get the secure environment access, so at that point it’s entirely your own fault, if you get exploited.
I’m out of touch here, what happened? No longer use it, but have some previously stored data there, should I do a purge? Is it dead or did they transition to something profit-driven and questionable?