How to Fix Insecure Cloud Storage Buckets in Vibe-Coded Apps

Quick answer

Insecure cloud storage buckets are a common security flaw in vibe-coded apps, where AI tools like Cursor, Bolt.new, or v0 generate code that uses public buckets or weak access controls. The fix is to audit bucket policies, set private ACLs, and use signed URLs for user access. OverMCP’s free scanner can detect exposed buckets in seconds.

What to check first

Before deploying, run through this checklist to catch bucket misconfigurations:

Step-by-step fix

1. Audit existing bucket permissions

Use the cloud provider’s CLI to check who can access the bucket. For AWS S3:

aws s3api get-bucket-acl --bucket your-bucket-name
aws s3api get-bucket-policy --bucket your-bucket-name

If the ACL includes AllUsers or AuthenticatedUsers, the bucket is public. For GCS:

gsutil iam get gs://your-bucket-name

Look for allUsers or allAuthenticatedUsers in the bindings.

2. Block public access by default

Set the bucket to private. For S3, you can block all public access:

aws s3api put-public-access-block --bucket your-bucket-name --public-access-block-configuration BlockPublicAcls=true,IgnorePublicAcls=true,BlockPublicPolicy=true,RestrictPublicBuckets=true

For GCS:

gsutil iam ch -d allUsers gs://your-bucket-name
gsutil iam ch -d allAuthenticatedUsers gs://your-bucket-name
gsutil defacl set private gs://your-bucket-name

3. Use signed URLs for user access

Never expose bucket objects directly. Generate time-limited signed URLs in your backend. Example with AWS SDK (Node.js):

import { S3Client, GetObjectCommand } from "@aws-sdk/client-s3";
import { getSignedUrl } from "@aws-sdk/s3-request-presigner";

const s3 = new S3Client({ region: "us-east-1" });
const command = new GetObjectCommand({ Bucket: "your-bucket", Key: "user-file.pdf" });
const signedUrl = await getSignedUrl(s3, command, { expiresIn: 3600 }); // 1 hour

For Supabase storage, use the built-in signed URL method:

const { data, error } = await supabase
  .storage
  .from('avatars')
  .createSignedUrl('public/avatar1.png', 60); // 60 seconds

4. Enable encryption

Ensure server-side encryption is active. For S3, enable default encryption:

aws s3api put-bucket-encryption --bucket your-bucket-name --server-side-encryption-configuration '{"Rules":[{"ApplyServerSideEncryptionByDefault":{"SSEAlgorithm":"AES256"}}]}'

5. Set up monitoring

Enable CloudTrail (AWS) or audit logs (GCP) to track bucket access. Set alarms for suspicious activity.

6. Scan your codebase

AI coding tools may leave bucket names and URLs in comments or config files. Run a free AI app security scanner to detect exposed endpoints.

Common mistakes

Vibe-coded apps often skip these steps because AI models are trained on best practices but rarely enforce them. A quick scan with OverMCP’s continuous security monitoring can catch these issues pre-deployment.

FAQ

How do I know if my cloud storage bucket is public?

Check the bucket’s ACL and policy via CLI or cloud console. Look for AllUsers or allUsers permissions. You can also use OverMCP’s security headers checker to inspect your app’s asset URLs.

Can I use signed URLs with Supabase storage?

Yes, Supabase storage provides a createSignedUrl method. Always use it for user-facing access instead of making the bucket public.

What’s the risk of an insecure bucket in a vibe-coded app?

Attackers can list, download, or upload files, leading to data breaches, malware hosting, or increased cloud costs. For example, exposed S3 buckets have led to massive leaks of user data.