Ah so I just dug into the rules. What happened was a plugin made a DNS request to mozilla.cloudflare-dns.com. I've nothing special set up for Firefox, but basically no rules for plugin-container, so when a plugin tries to make a DNS request Little Snitch pops up an alert.
Not great I suppose, but better than nothing. Generally what I'll see for Firefox itself are requests for non 80/443 ports.
Not great I suppose, but better than nothing. Generally what I'll see for Firefox itself are requests for non 80/443 ports.