- Platform: Android
- Weakness: MASWE-0002
- Weakness in the numbering of the MASWE beta: MASWE-0007
- Profiles: L1 (basic security), L2 (advanced security)
- Type: static, code, manual
- APIs:
Environment#getExternalStoragePublicDirectory,Environment#getExternalStorageDirectory,Environment#getExternalFilesDir,Environment#getExternalCacheDir,MediaStore,WRITE_EXTERNAL_STORAGE,MANAGE_EXTERNAL_STORAGE - Knowledge: MASTG-KNOW-0042
Overview
This test uses static analysis to look for uses of APIs allowing an app to write to locations that are shared with other apps (MASTG-TEST-0001) such as the External Storage APIs or the MediaStore API as well as the relevant Android manifest storage-related permissions.
Some APIs used to write to shared storage include getExternalStoragePublicDirectory, getExternalStorageDirectory, getExternalFilesDir, or MediaStore. Permissions include WRITE_EXTERNAL_STORAGE, and MANAGE_EXTERNAL_STORAGE. See MASTG-KNOW-0042 for more information on these APIs and permissions.
Note
This static test is great for identifying all code locations where the app is writing data to shared storage. However, it does not provide the actual data being written, and in some cases, the actual path in the device storage where the data is being written. Therefore, it is recommended to combine this test with others that take a dynamic approach, as this will provide a more complete view of the data being written to shared storage.
Steps
- Use MASTG-TECH-0013 to reverse engineer the app.
- Use MASTG-TECH-0014 to look for the relevant APIs.
- Use MASTG-TECH-0117 to obtain the AndroidManifest.xml.
- Use MASTG-TECH-0126 to obtain the relevant permissions.
Observation
The output should contain a list of APIs and storage-related permissions used to write to shared storage and their code locations.
Evaluation
The test case fails if all of the following apply:
- the app has the proper permissions declared in the Android manifest (e.g.
WRITE_EXTERNAL_STORAGE,MANAGE_EXTERNAL_STORAGE, etc.) - the app uses APIs that write to shared storage (e.g.
getExternalStoragePublicDirectory,getExternalStorageDirectory,getExternalFilesDir,getExternalCacheDir,MediaStore, etc.) - the data being written to shared storage is sensitive and not encrypted.
Further Validation Required:
Inspect each reported code location using MASTG-TECH-0023 to determine whether the data is sensitive:
- Determine whether the data written to shared storage includes sensitive information (e.g., personal data, credentials, or tokens).
- Determine whether the data is stored without encryption.
- OWASP -
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- OWASP Mobile Application Security Weakness Enumeration (MASWE) v1.0.0, August 2026, from OWASP/maswe: © The OWASP Foundation, licensed under CC BY-SA 4.0. Changes: converted into the GRCA format, the wording unchanged, linked to the MASVS controls they map to. These adaptations are shared under CC BY-SA 4.0 as well.
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- OWASP Mobile Application Security Testing Guide (MASTG) v2.0.0, Juni 2026, aus OWASP/mastg: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Nur die Tests und Best Practices, ohne Codebeispiele, Bilder, Werkzeuge und Apps. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert; Verweise auf andere Seiten des MASTG als Links zu mas.owasp.org; die Schwachstelle jedes Tests in der Nummerierung der MASWE v1 und mit ihr verknüpft. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
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