Simon Willison’s Weblog

How an empty S3 bucket can make your AWS bill explode (via) Maciej Pocwierz accidentally created an S3 bucket with a name that was already used as a placeholder value in a widely used piece of software. They saw 100 million PUT requests to their new bucket in a single day, racking up a big bill since AWS charges $5/million PUTs.

It turns out AWS charge that same amount for PUTs that result in a 403 authentication error, a policy that extends even to "requester pays" buckets!

So, if you know someone's S3 bucket name you can DDoS their AWS bill just by flooding them with meaningless unauthenticated PUT requests.

AWS support refunded Maciej's bill as an exception here, but I'd like to see them reconsider this broken policy entirely.

Update from Jeff Barr:

We agree that customers should not have to pay for unauthorized requests that they did not initiate. We’ll have more to share on exactly how we’ll help prevent these charges shortly.

AWS Fixes Data Exfiltration Attack Angle in Amazon Q for Business. An indirect prompt injection (where the AWS Q bot consumes malicious instructions) could result in Q outputting a markdown link to a malicious site that exfiltrated the previous chat history in a query string.

Amazon fixed it by preventing links from being output at all—apparently Microsoft 365 Chat uses the same mitigation. # 19th January 2024, 12:02 pm