HOW TO FIND THE AWS ACCOUNT ID OF ANY S3 BUCKET

Summary from the TLDR Web Dev newsletter

A new technique can discover the AWS Account ID associated with any S3 bucket regardless of whether it is public or private. The technique leverages the fact that CloudTrail logs will record requests permitted by a VPC Endpoint policy but blocked by other policies. Whether AWS account IDs are considered sensitive information is still up in the air, but this technique could potentially be used to uncover other resource identifiers beyond AWS account IDs.