I know what Cloudflare is but i don't quite understand the underlying issue.
Can someone explain in simpler terms what happened here and how it a) affects sites using Cloudflare and b) Users accessing sites with Cloudflare?
Can someone explain in simpler terms what happened here and how it a) affects sites using Cloudflare and b) Users accessing sites with Cloudflare?
As one such server handles many sites, everything that the server handled before that request may be compromised. This includes all HTTP-GET/POST data (credentials, direct messages to other users, ...), Headers (API tokens, Login-Cookies) and contents.
So, you have to assume that everything you did on a CF "protected" website in the last months (especially between 2017-02-13 and 2017-02-17) is potentially compromised.