Something's up with AWS SNS?
I mean, in my previous workplace I found an SNS topic just bluntly with overly permissions allowing anyone with an AWS account to do literally anything.
And in my new workplace I have found just the same.
This require investigation I'm too lazy to do, but sounds like there's an insecure default policy that is deployed here.
If SNS had a public URL like S3 buckets do, it'd have been an easy job. But recon here is a little bit harder.
Tho, still, if you discover one it can be devastating.