QR / NFC Scan -> Privileged Action Without Confirmation

← Native / WebView Bridge (JS <-> Native)

qr_nfc_to_privileged_action   MEDIUM

Description

A scanned QR/NFC tag from an untrusted caller is forwarded straight to a privileged action / automation trigger with no user confirmation, so a co-resident app or a planted tag executes it silently (Home Assistant Companion GHSA NFC/QR class).

How it works

A scanned QR code or tapped NFC tag carries a payload naming a privileged automation. The app forwards that payload straight to the action dispatcher with no authentication of the scan source and no explicit user confirmation, so a planted/overwritten NFC tag fed by a co-resident app silently triggers the automation (Home Assistant Companion GHSA NFC/QR class). This is an offline, deterministic simulation: a scan event carries its source, caller trust, and payload. The secure path requires both a trusted scan source and an explicit user confirmation before firing.

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 Native / WebView Bridge (JS <-> Native) category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an emulator/simulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: frida, objection · Android: jadx, adb, drozer · iOS: ipsw, class-dump.
2. Locate the target. From the home index, open QR / NFC Scan -> Privileged Action Without Confirmation (qr_nfc_to_privileged_action). 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. Reach the JS<->native bridge (or the framework/plugin API) from untrusted web content / a cross-origin iframe / a malicious provider, and confirm the privileged native call fires with no main-frame/origin, callback-id, or permission gate in between.
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.

Tools (optional)

• frida
• objection

Android

• jadx
• adb
• drozer

iOS

• ipsw
• class-dump

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 QR
• crafted NFC tag

Real-world references

Concrete public disclosures that match this vulnerability class:

• GHSA (Home Assistant NFC/QR silent automation)