How is your web browser even accessing the internet without any firewall permissions? Maybe worth checking your Windows Firewall rules & double-check what is already in there for LibreWolf.

Or maybe your web browser just updated itself, or the previous firewall rule was removed after a Windows update? More questions than answers :P

Though for what it’s worth your browser technically doesn’t need any firewall permissions if you’re piping it through a local proxy e.g. Tor.