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MASWE-0006: Sensitive Data Stored Unencrypted in Private Storage Locations

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Mobile apps may need to store sensitive data locally within private storage locations such as the application sandbox and this data is at risk of exposure via, for example, incorrect file permissions, an app vulnerability, device vulnerability or data backup mechanisms.

Sensitive data may include personally identifiable information (PII), passwords, cryptographic keys or session tokens.


  • Loss of Confidentiality: Under the right conditions an attacker could extract sensitive data stored internally within the application sandbox leading to loss of confidentiality and enable further attacks such as identity theft or account takeover.

Modes of Introduction

  • Data Stored Unencrypted: Sensitive data is written to the app's private data directory (sandbox) unencrypted.
  • Hardcoded Encryption Key: Sensitive data is encrypted but the key is hardcoded inside the application.
  • Encryption Key Stored on Filesystem: Sensitive data is encrypted but the key is stored alongside it or in another easily accessible location.
  • Encryption Used is Insufficient: Sensitive data is encrypted but the encryption is not considered to be strong.


  • Avoid storing sensitive data locally if not required for application functionality to reduce the likelihood and impact of this weakness. For example keeping PII server-side, rendering it at time of use, and removing any cached data on logout.
  • Store cryptographic keys exclusively using the platform's hardware-backed keystore solution, such as the Android Keystore or the iOS Keychain.
  • For storing other files and preferences, use platform-provided features for encrypting data at rest or other techniques implementing envelope encryption with Data Encryption Keys (DEK) and Key Encryption Keys (KEK) or equivalent methods. For example, on Android, use EncryptedFile or EncryptedSharedPreferences; on iOS, use iOS Data Protection.