Dynamic BroadcastReceiver Exposure

← Improper Platform Usage

dynamic_broadcast_receiver_exposure   MEDIUM

Description

A runtime-registered receiver (registerReceiver() without RECEIVER_NOT_EXPORTED / a signature permission) is implicitly exported, so any co-resident app can send it a crafted broadcast to trigger sensitive functionality, or the app receives an untrusted broadcast and leaks data. Distinct from manifest-declared exported receivers: the dynamic registration flags are the boundary (Android MASTG-TEST-0366 class).

How it works

A receiver registered at runtime with registerReceiver() but without RECEIVER_NOT_EXPORTED (API 33+) and without a signature permission is implicitly exported. Any co-resident app can then forge a crafted broadcast to drive sensitive functionality, here a promo-apply broadcast that grants store credit. The registration flags are the boundary, distinct from manifest exported receivers (Android MASTG-TEST-0366). On Android, DVMA registers such a runtime receiver and the companion attacker forges the broadcast; this screen reads back what was applied. The secure path registers RECEIVER_NOT_EXPORTED and requires a signature permission the attacker package does not hold, so the forged broadcast is dropped.

How to exercise it. DVMA is the harness - open this module from the home index and tap the demo action. The screen ships the malicious input and simulates the attacker (e.g. the companion app, crafted intent, or scanned payload) in-process, and the evidence panel prints the proof. The Tools (optional) and Attack inputs below are only needed to reproduce the exploit end-to-end on a real device.

Exploit steps

1. Set up. Build DVMA with a flavor that enables the Improper Platform Usage category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an Android emulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: adb, drozer, jadx.
2. Locate the target. From the home index, open Dynamic BroadcastReceiver Exposure (dynamic_broadcast_receiver_exposure). The How it works section above describes this module’s specific weakness; the screen states the intended-secure behavior and exposes the vulnerable action.
3. Exploit. From a co-resident/attacker context (adb shell am start/drozer, or a crafted deep link / QR), send the untrusted input to the exported component or WebView and confirm the app performs the unsafe action (navigation, JS execution, file/URI access) with no validation.
4. Observe the evidence. Trigger the vulnerable action and read the evidence panel - it prints the concrete proof (leaked value, accepted replay, executed payload, or unauthorized result).
5. Contrast with the secure path. Run the module’s secure/hardened action (where provided) and confirm the same attack is rejected - this is what a correct implementation should do.
6. Map it back. Cross-reference the MASTG v2 test(s) MASTG-TEST-0366 for the canonical procedure and remediation.

Tools (optional)

• adb
• drozer
• jadx

Attack inputs

Payloads/artifacts you author for the on-device attack. The demo already ships and simulates these in-process (e.g. the malicious companion app / crafted intent is emulated inside the screen), so you only need to craft them to reproduce the exploit on a real device:

• crafted broadcast

Real-world references

Concrete public disclosures that match this vulnerability class:

• OWASP MASTG-TEST-0366: exported and unprotected broadcast receivers