Just to clarify and avoid confusion, since I can see a lot of misinformation about this already, even though that post covers it mostly, I'll reiterate a bit on what happened.
A provider Discord and various other websites (Some of them fairly large), called CloudFlare, had a bug in their code which disclosed bits of memory when handling a malformed request. In short, this caused various potentially sensitive things to get mistakenly leaked, such as login tokens, and more rarely, login details themselves.
Currently, it appears to be fairly contained, and as far as I can tell, it's not been abused en-masse just yet.
I would personally reccomend to change your password on websites that are using cloudflare (Discord being one of them), just as a general precaution, as usually this will cause login tokens to be invalidated for the service as well.
You don't have to, and the chances you'll see anything happen to you or your accounts are slim, but if you care about your online accounts, then I'd suggest changing passwords, rather then waiting to see if you've been compromised.
I would also reccomend to look into getting a password manager. (Example: 1Password or LastPass) - So you can have different, random passwords for every service, thus avoiding all of your accounts being compromised if just one of them is.