Deep Link -> Trusted WebView Navigation

← Improper Platform Usage

deeplink_to_webview_navigation   MEDIUM

Description

A URL parameter from an incoming deep link/intent is loaded straight into a trusted WebView with no origin allowlist, so an attacker renders arbitrary content in-app (TikTok CVE-2024-45240 / Rakuten CVE-2024-41918 / EcoOnline CVE-2026-26897 class).

How it works

An incoming deep link carries a url parameter that the app loads directly into a trusted in-app WebView. Because there is no origin allowlist, any origin, and even javascript: or file:// URLs, is rendered inside the app’s security context (shared session and cookies, JS bridges), enabling phishing and local-file or JS execution (the CVE-2026-26897 class). On Android the resolved URL is navigated into a real trusted in-app WebView, rendering it inside the app security context. The secure router allows only first-party https origins and rejects everything else.

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 emulator/simulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: Android: adb, drozer, jadx · iOS: xcrun simctl openurl, idb.
2. Locate the target. From the home index, open Deep Link -> Trusted WebView Navigation (deeplink_to_webview_navigation). 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-0332, MASTG-TEST-0027 for the canonical procedure and remediation.

Tools (optional)

Android

• adb
• drozer
• jadx

iOS

• xcrun simctl openurl
• idb

Real-world references

Concrete public disclosures that match this vulnerability class:

• CVE-2026-22072 (OPPO arbitrary URL -> WebView token theft)
• CVE-2024-45240 (TikTok deep-link -> LynxView WebView takeover)
• CVE-2026-26897 (EcoOnline EHS deep-link validation bypass -> WebView open redirect)