Due to HN's flaky Cloudflare 503 Bad Gateway error, I noticed that Cloudflare is also being affected by S3 being down in a similar but subtle way. See their status page's broken logo on the upper left hand corner.[1] It was actually directly linking to a S3 URL: https://s3.amazonaws.com/statuspage-production/pages-transac...
All websites that use Cloudflare were potentially affected by Cloudbleed which is what makes it such a terrible thing.
You will never know the exact damage, the only thing you can do to play it 100% safe is to rotate all credentials on sites using Cloudflare.
And you can't access HN without going through Cloudflare (unfortunately, but HN is having a hard enough time to keep up with traffic as it is, without Cloudflare it would perform a lot worse than it does).
[1]: https://www.cloudflarestatus.com/