WebView SOP / CSP Disabled (Cross-Origin & Inline Script)

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

webview_sop_csp_disabled   HARD

Description

The app’s WebView relaxes/omits Same-Origin-Policy and Content-Security-Policy enforcement (e.g. allowUniversalAccessFromFileURLs / allowFileAccessFromFileURLs, no CSP on loaded content), so cross-origin reads and inline/injected script execute in the trusted app origin (WebKit SOP-bypass CVE-2026-20643 / CSP-bypass CVE-2026-20665 app-level analog).

How it works

The app’s WebView relaxes/omits Same-Origin-Policy and Content-Security-Policy (allowUniversalAccessFromFileURLs true, no CSP), so a file:// page can read a cross-origin resource and run inline/injected script in the trusted app origin (WebKit SOP-bypass CVE-2026-20643 / CSP-bypass CVE-2026-20665 app-level analog). This writes real files and loads them in a real WebView with universal file access on and no CSP, so the page reads a cross-origin resource and inline script exfiltrates it (the in-memory panel is the offline contrast). The secure config (universal access off, restrictive CSP) blocks the cross-origin read and refuses inline script.

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: mitmproxy, r2frida, frida · Android: jadx · iOS: ipsw, class-dump.
2. Locate the target. From the home index, open WebView SOP / CSP Disabled (Cross-Origin & Inline Script) (webview_sop_csp_disabled). 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.
6. Map it back. Cross-reference the MASTG v2 test(s) MASTG-TEST-0335, MASTG-TEST-0333 for the canonical procedure and remediation.

Tools (optional)

• mitmproxy
• r2frida
• frida

Android

• jadx

iOS

• ipsw
• class-dump

Real-world references

Concrete public disclosures that match this vulnerability class:

• About the security content of iOS 26.4 (CVE-2026-20643 SOP bypass / CVE-2026-20665 CSP bypass)