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HIGHOpSec

OPSEC-MICROSOFT-SAS-2023

Cloud · Microsoft Azure Storage

Summary

Microsoft's AI research team shared open-source training data via an Azure Storage Shared Access Signature (SAS) token committed to a public GitHub repo around July 2020. The token was misconfigured to scope access to the entire storage account with full-control permissions instead of the intended read-only bucket, so anyone with the link could view, delete, and overwrite files. Wiz researchers discovered it in June 2023, finding 38 terabytes of exposed internal data including two employees' workstation disk backups with secrets, private keys, passwords, and over 30,000 internal Teams messages. Writable pickle-format models created a model-poisoning supply-chain risk; Microsoft revoked the token and reported no customer data was exposed.

How to avoid it in your code

  • Use service or user-delegation SAS scoped to a single container/blob, never an account-level SAS.
  • Grant read-only access and expire SAS tokens in minutes or hours, never years.
  • Never commit SAS URLs or storage credentials to a repository; serve shared data via a controlled endpoint.
  • Enable secret scanning that flags SAS tokens with broad scope, full permissions, or distant expiry.
  • Prefer user-delegation SAS tied to Entra identities so tokens can be centrally revoked and audited.

References

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