The fact that the challenge is currently not working for Waterfox Classic and Pale Moon is not by intent, and we do not want to be in the business of saying one browser is more legitimate than another. This feature attempts to determine browser versus non-browser traffic and block non-browsers. This looks like a bug with our 'Managed Challenge' security action that's causing the loop. I hope this issue will be heard, fixed and never be repeated again. There's no transparency and no accountability to their actions. They prevent users of these browsers from accessing millions of websites with a flip of a switch. A 3rd party corporation is deliberately deciding which browsers are legitimate and which are not.

That'd between visitors and owners of that web site, and completely understandable. Let me be clear, this is not a case of a web site owner deciding to use a recent feature that's not supported by these browsers.

Visitors are told to contact respective web site owners and forum threads are locked quickly. Some users have posted at Clodflare community forum to no avail and Cloudflare support is only available to paid customers. Ghacks' post has a good summary of related links and an active discussion at comments section, though the 'protection' got more strict in the meantime thus the mentioned workaround isn't effective anymore. Users of Waterfox Classic and Pale Moon browsers have been reporting that they're stuck in an infinite loop of Cloudflare's infamous 'checking your browser' screen and can't access web sites that enabled Cloudflare's browser integrity check feature.

Waterfox classic