Vault 3 for Android documents are stored on your device. By default, they are stored in this folder: "/sdcard/Vault 3 Documents". Other applications can access files stored there.
Vault 3 for Android does not transmit any user data to remote servers.
Vault 3 for Android documents are optionally password-protected with AES encryption and 256-bit keys.
While Vault 3 for Android passwords can optionally be cached in RAM, they are never persisted to permanent storage.
Recommendations:
Always password-protect Vault 3 for Android documents containing sensitive information.
Protect your device with a PIN code, especially if you enable password caching.
If you have multiple encrypted Vault 3 for Android documents, make sure each document has a unique password.