Cloudflare's Browser Intergrity Check/Verification/Challenge feature used by many websites, is denying access to users of non-mainstream browsers like Pale Moon.
Users reports began on January 31:
https://forum.palemoon.org/viewtopic.php?f=3&t=32045
This situation occurs at least once a year, and there is no easy way to contact Cloudflare. Their "Submit feedback" tool yields no results. A Cloudflare Community topic was flagged as "spam" by members of that community and was promptly locked with no real solution, and no official response from Cloudflare:
https://community.cloudflare.com/t/access-denied-to-pale-moo...
Partial list of other browsers that are being denied access:
Falkon, SeaMonkey, IceCat, Basilisk.
Hacker News 2022 post about the same issue, which brought attention and had Cloudflare quickly patching the issue:
https://news.ycombinator.com/item?id=31317886
A Cloudflare product manager declared back then: "...we do not want to be in the business of saying one browser is more legitimate than another."
As of now, there is no official response from Cloudflare. Internet access is still denied by their tool.