TL;DR Some hosting providers implemented http-01 having one part of the challenge key reflected in the response. This resulted in a huge amount of websites being vulnerable to XSS just because of their implementation of the http-01 ACME-challenge.
When we think about cyber attacks, we usually think about the malicious actors behind the attacks, the people who profit or gain from exploiting digital vulnerabilities and trafficking sensitive data. In doing so, we can make the mistake of ascribing the same humanity to their methods, thinking of people sitting in front of laptops, typing code into a terminal window.
TL;DR Bucket upload policies are a convenient way to upload data to a bucket directly from the client. Going through the rules in upload policies and the logic related to some file-access scenarios we show how full bucket object listings were exposed with the ability to also modify or delete existing files in the bucket.