I deployed the new Cloudflare Wordpress Plugin on my website earlier this week. Although I have a page rule telling cloudflare not to cache my simple machines forum-based forum, the plugin caused serious problems for forum users. They were unable to log in, they were sometimes logged out, and they sometimes appeared to log in as different users in the same rights group, although they were not able to post as another user. I verified this behavior in Chrome, Opera, Firefox, and Edge.
Users also experienced Wordpress login issues. I use a source optimization plugin called autoptimize and the owner suggested that Cloudflare’s caching of nonce in HTML could cause problems. I changed some settings and was able to solve that problem by preventing caching and optimization, but didn’t like the hit to performance.
I hope these issues can be solved, because I would love to use the plugin.