Apparently os-prober is a security risk but tbh I don’t really understand the issue. I’ve read its something to do with mounting all partitions as root, but you have to run grub-mkconfig as root anyway so I don’t see how that could be used to gain root privileges? Does it not unmount them afterwards? And could you avoid the risk by just disabling it again after you’ve generated your grub.cfg?
The other option seems to be manually adding a Windows entry to /etc/grub.d/40_custom so I assume thats the recommended way to dual boot?
It’s, as you said, because it mounts everything as root. It’s possible that this could be exploited to gain root privileges but not likely. If you’re paranoid and/or building a secure system that you don’t need to dual boot, it’s not a bad idea to disable it.