I've seen that reported once or twice. It appears that some device on your network was generating random IP addresses and Serviio was capturing them. Windows will self-assign an IP address if it loses contact with the DHCP server. No, I don't think anyone is accessing your network through Serviio. If you don't have port 23424 forwarded in your firewall to your Serviio computer, then nothing can reach your server. And even if that port is forwarded, it's only accessing the web server function that provides access to MediaBrowser, and that isn't connected through your computer system in any other way.
It's also possible your DHCP server had a hiccup in some way that changed the IP address range and was temporarily issuing incorrect addresses. Electronic devices seem to have a mind of their own at times.
