Websites should avoid using Cloudflare.
Cloudflare’s HTTP fronting service incorporates some seriously questionable practices. As things stand, the extent of the number of websites which have come to use Cloudflare, multiplied by its issues, poses a hazard to the state of the web.
Cloudflare as advertised to site operators fails to identify these issues, and operators may even be unaware of them.
https://www.devever.net/~hl/cloudflare
https://www.devever.net/~hl/contact