A severe vulnerability was announced by the WordPress Security Team that allows unauthenticated users to change content on a site using unpatched (below version 4.7.2) WordPress.
The problem was found by the team at Sucuri and reported to WordPress. The WordPress team worked with WAF vendors, including Cloudflare, to roll out protection before the patch became available.
Earlier this week we rolled out two rules to protect against exploitation of this issue (both types mentioned in the Sucuri blog post). We have been monitoring the situation and have not observed any attempts to exploit this vulnerability before it was announced publicly.
Customers on a paid plan will find two rules in WAF, WP0025A and WP0025B, that protect unpatched WordPress sites from this vulnerability. If the Cloudflare WordPress ruleset is enabled then these rules are automatically turned on and blocking.