Spam from specific user agent

I’ve been getting thousands of requests each day from a specific user agent, Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Firefox/38.0. They’re all from different ip addresses (the ones I’ve looked up have been Google LLC and Cloudflare), and they all use that exact same user agent. nginx logs So far I’ve seen 90 unique ip addresses

ip count

I’ve started giving 403 statuses back to them, since it seems like something is wrong here, but I can’t trace them back to any one specific point. They all seem to be legitimate requests, but they’re just so suspicious with the amount of servers they’re coming from. Am I missing something here?