yea this is almost certainly a misconfigured cloudflare configuration - did you (or anyone else) make any recent changes in the cloudflare dashboard? like @itsbhanusharma said, i would disable the proxy cloud first to see if that fixes it temporarily (may have to wait a few minutes or clear your brower cache).
if cloudflare was recently setup, i would also make sure rocket loader isn’t enabled on cloudflare and SSL/TLS encryption mode is set to Full (Strict). make sure you have the cloudflare template configured properly in your app.yml file.