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Run npx skillmds@latest add noorqureshi/cloud-s3-exposure in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Who published Cloud S3 Exposure?

NoorQureshi (@noorqureshi) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Cloud S3 Exposure by noorqureshi — Agent Skill

Name: Cloud S3 Exposure
Author: NoorQureshi

Cloud S3 Exposure

Find and prove misconfigured cloud object storage (S3/GCS/Azure Blob). Load when assets load from *.s3.amazonaws.com, storage.googleapis.com, *.blob.core.windows.net, bucket-looking hostnames, or "bucket". Signals: public-read/list, unauthenticated writes, predictable bucket names.

NoorQureshi 33bc73a 2.1 KB Updated Sep 17, 2026

File contents

Cloud object-storage misconfiguration

When it applies

The app stores files in S3/GCS/Azure Blob and the bucket's ACL/policy is too open — public listing, public read of private objects, or (worst) unauthenticated write.

Why it works

Object-storage ACLs are easy to get wrong: "public" gets applied at the bucket level, or an IAM policy grants s3:ListBucket/GetObject/PutObject to *. Predictable names (companyname-backups, -assets, -dev) make discovery trivial.

Method

Find bucket names: from asset URLs, JS, DNS CNAMEs, and permutations of the org name (company, company-prod, company-backups, region suffixes).
Test list/read (S3): aws s3 ls s3://bucket --no-sign-request (list) and aws s3 cp s3://bucket/file . --no-sign-request (read). --no-sign-request = anonymous.
Test write (high impact, do carefully & in scope): aws s3 cp poc.txt s3://bucket/ --no-sign-request — a successful anonymous write is critical (defacement/malware hosting).
GCS/Azure: gsutil ls gs://bucket / anonymous HTTPS GET; Azure ?comp=list on the container.
Scale carefully with s3scanner/gcpbucketbrute on name lists — respect scope & rate.

Gotchas

403 on the bucket root ≠ safe — individual objects may still be public; test known object paths.
Anonymous write is the crown jewel but easy to over-test — upload one harmless marker, then stop.
Region matters for the endpoint; a wrong region gives misleading 301/403.

Verify success

Anonymous listing/read of non-public objects, or a successful anonymous write of a harmless proof file (then remove it). Capture the exact command + response.

References

AWS S3 security docs; "hacking the cloud" S3 guides; s3scanner README.

---name: cloud-s3-exposuredescription: Find and prove misconfigured cloud object storage (S3/GCS/Azure Blob). Load when assets load from *.s3.amazonaws.com, storage.googleapis.com, *.blob.core.windows.net, bucket-looking hostnames, or "bucket". Signals: public-read/list, unauthenticated writes, predictable bucket names.---# Cloud object-storage misconfiguration## When it appliesThe app stores files in S3/GCS/Azure Blob and the bucket's ACL/policy is too open — publiclisting, public read of private objects, or (worst) unauthenticated write.## Why it worksObject-storage ACLs are easy to get wrong: "public" gets applied at the bucket level, or anIAM policy grants `s3:ListBucket`/`GetObject`/`PutObject` to `*`. Predictable names(`companyname-backups`, `-assets`, `-dev`) make discovery trivial.## Method1. **Find bucket names**: from asset URLs, JS, DNS CNAMEs, and permutations of the org name (`company`, `company-prod`, `company-backups`, region suffixes).2. **Test list/read (S3)**: `aws s3 ls s3://bucket --no-sign-request` (list) and `aws s3 cp s3://bucket/file . --no-sign-request` (read). `--no-sign-request` = anonymous.3. **Test write** (high impact, do carefully & in scope): `aws s3 cp poc.txt s3://bucket/ --no-sign-request` — a successful anonymous write is critical (defacement/malware hosting).4. **GCS/Azure**: `gsutil ls gs://bucket` / anonymous HTTPS `GET`; Azure `?comp=list` on the container.5. **Scale carefully** with `s3scanner`/`gcpbucketbrute` on name lists — respect scope & rate.## Gotchas- 403 on the bucket root ≠ safe — individual objects may still be public; test known object paths.- Anonymous write is the crown jewel but easy to over-test — upload one harmless marker, then stop.- Region matters for the endpoint; a wrong region gives misleading 301/403.## Verify successAnonymous listing/read of non-public objects, or a successful anonymous write of a harmlessproof file (then remove it). Capture the exact command + response.## ReferencesAWS S3 security docs; "hacking the cloud" S3 guides; s3scanner README.

Frequently asked questions