App Clip Invocation Injection

← Improper Platform Usage

app_clip_invocation_injection   MEDIUM

Description

An App Clip acts on its invocation parameters (invocation URL / NFC / QR / associated-domain payload) - performing a purchase, order, or account action - while TRUSTING that the invocation came from a legitimate physical trigger and INHERITING authentication state as if it were the full app, so a crafted invocation URL drives a privileged action without the auth the full app would require. The invocation payload is attacker-controllable and must be treated as untrusted. The secure path validates the invocation against the associated domain, re-authenticates sensitive actions, and never inherits full-app trust (iOS App Clip class).

How it works

An App Clip acts on its invocation parameters (invocation URL, NFC, QR, or banner) and performs a purchase while trusting that the invocation came from a legitimate physical trigger and inheriting authentication state as if it were the full app. A crafted invocation URL from a look-alike domain drives a high-value payment with no re-auth. The invocation URL is parsed and validated against the same real bundled apple-app-site-association.json as the Universal Link module. The secure path requires the invocation host to equal the associated domain and the path to match a real AASA component, re-authenticates sensitive actions, and never inherits full-app trust.

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 iOS simulator / a device you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: ipsw, Hopper.
2. Locate the target. From the home index, open App Clip Invocation Injection (app_clip_invocation_injection). 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 an attacker context (a crafted custom-URL-scheme / Universal Link, a malicious document provider / share extension, or a Shortcut), send the untrusted input to the handler and confirm the app performs the unsafe action (navigation, file/URL access, privileged operation) 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.

Tools (optional)

• ipsw
• Hopper

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 App Clip invocation URL
• spoofed QR/NFC invocation

Real-world references

Concrete public disclosures that match this vulnerability class:

• Apple: Responding to App Clip invocations