For those interested in this in general, here is the list of domains using Cloudflare services that are possibly affected by this issue: https://github.com/pirate/sites-using-cloudflare. There are some very popular sites on that list.
An important step to take in this situation is to log out of any of those sites that you regularly visit to clear your session information; then change passwords. (And consider enabling two factor authentication on them if they support it.)
Glad to see Moodle stepping up and informing people about this!