# Deep link auto-triggers sensitive action

BROWSABLE deep links or intents that start mic, assistant, or messaging without a user confirmation step

_Area: Mobile app security. Seen in 3 disclosed reports; 3 confirmed bounties, median $3,134, range $2,250-$3,134; latest 2025-10-23. Updated 2026-10-23._

## How it works
A public entry point (a BROWSABLE deep link or an implicit intent) is wired straight to a sensitive capability, and the app treats "the intent arrived" as equivalent to "the user asked for this." The consent step that normally sits between the two — a mic tap, a send confirmation — is skipped on that path. Any webpage or installed app that can fire the entry point therefore drives the capability on the user's behalf.

## Where it shows up
- BROWSABLE deep links or `market://`-style intents that launch a privileged app and auto-activate the microphone or listening mode [E1](https://bugbountylibrary.com/r/blog%3Afeed-bugs-xdavidhu-me-bugs-0011.md)[E2](https://bugbountylibrary.com/r/blog%3Andevtk-github-io-writeups-2025-08-30-assistant.md)
- Assistant/voice flows that accept device-played audio (TTS, Web Speech API) as user commands without checking the source [E1](https://bugbountylibrary.com/r/blog%3Afeed-bugs-xdavidhu-me-bugs-0011.md)[E2](https://bugbountylibrary.com/r/blog%3Andevtk-github-io-writeups-2025-08-30-assistant.md)
- `ACTION_SENDTO` handlers for `sms:`/`smsto:`/`mms:`/`mmsto:` that send immediately instead of showing a prefilled confirmation UI [E3](https://bugbountylibrary.com/r/blog%3Atowerofhanoi-it-writeups-cve-2025-12080.md)
- Small-screen or companion variants (Wear OS) of an app that drop the consent screen the phone version has [E3](https://bugbountylibrary.com/r/blog%3Atowerofhanoi-it-writeups-cve-2025-12080.md)
- Intent handlers that perform the action in `onCreate`/`onNewIntent` before any user interaction

## How to review
Trace every exported/BROWSABLE entry point to the sensitive sink it reaches. The invariant: a sensitive action (mic capture, sending a message, sharing location) must be gated by an explicit, in-app user confirmation that cannot be satisfied by the intent itself or by audio/text the caller supplies. Check that the confirmation UI is present on every variant, including Wear OS and other form factors [E3](https://bugbountylibrary.com/r/blog%3Atowerofhanoi-it-writeups-cve-2025-12080.md), and that launching via deep link lands on a prefilled, user-confirmable screen rather than executing. For voice, verify the assistant distinguishes trusted user speech from arbitrary device audio.

## Variants seen
- Webpage deep link auto-triggers Assistant listening; TTS audio then executes actions like sharing location [E1](https://bugbountylibrary.com/r/blog%3Afeed-bugs-xdavidhu-me-bugs-0011.md)
- `market://launch` BROWSABLE intent opens Assistant with mic already active, fed by Web Speech API [E2](https://bugbountylibrary.com/r/blog%3Andevtk-github-io-writeups-2025-08-30-assistant.md)
- `ACTION_SENDTO` on Wear OS Messages silently sends SMS/MMS from any installed app [E3](https://bugbountylibrary.com/r/blog%3Atowerofhanoi-it-writeups-cve-2025-12080.md)

## Why fixes fail
E1 established that Assistant should require a manual mic press on deep-link launch; E2 shows a different intent path (`market://launch`) still auto-activating the mic, so the consent gate was not applied uniformly across entry points [E1](https://bugbountylibrary.com/r/blog%3Afeed-bugs-xdavidhu-me-bugs-0011.md)[E2](https://bugbountylibrary.com/r/blog%3Andevtk-github-io-writeups-2025-08-30-assistant.md).

## Impact and severity
Silent message sending as the user, unauthorized location sharing, and device control via injected audio — high severity. Worse when the entry point is reachable from any webpage (no install needed) and when the action is irreversible, like an already-sent SMS [E3](https://bugbountylibrary.com/r/blog%3Atowerofhanoi-it-writeups-cve-2025-12080.md).

## Evidence
- E1: https://bugbountylibrary.com/r/blog%3Afeed-bugs-xdavidhu-me-bugs-0011.md
- E2: https://bugbountylibrary.com/r/blog%3Andevtk-github-io-writeups-2025-08-30-assistant.md
- E3: https://bugbountylibrary.com/r/blog%3Atowerofhanoi-it-writeups-cve-2025-12080.md