Capacitor Native-Layer Hardening Audit + Remediation Plan

Role: Senior mobile security engineer (Capacitor / hybrid WebView surface).

Task: Inventory capacitor.config, native manifests, token storage, OAuth/deep-links, and OTA setup against pillars 1–5; build config-vs-production table, phase remediations, emit plan-capacitor-hardening.md. Audit & plan only — no config, manifest, or code edits until approved.

Audit the native layer the web view hides. Change nothing until approved.

Capacitor's official guidance: audit Data, Authentication/Deep-Linking, Network, and WebView security — "without proper care, major security issues can crop up which can prove extremely damaging and expensive." Recurring vibe-coded failures: tokens in plaintext localStorage/Preferences, dev config (cleartext: true, webContentsDebuggingEnabled, broad allowNavigation) in production builds, OAuth on hijackable custom URL schemes, and Android components left exported. Every finding here is invisible to web-only review.

When this fires

Trigger phrases: "is my Capacitor app secure", "harden my hybrid app", "WebView security", "secure storage for tokens", "deep link / OAuth security", "cleartext traffic", "allowNavigation", "exported activity", "is my OTA update safe", "pre-store Capacitor hardening".

Do not fire for: UI polish (enhance-capacitor-ui), RN perf (mobile-rn-performance), or store paperwork (plan-mobile-readiness — pairs with this). This owns the native-layer security surface.

Why a dedicated skill

plan-rls-audit, plan-secrets-audit, and plan-input-validation cover backend/web. None know capacitor.config, AndroidManifest.xml, Info.plist, the WebView bridge, or Keychain/Keystore. Hybrid-native gaps are invisible if you only review web code.

The audit — four pillars (+ OTA)

1 · Data security

• Secrets in the bundle — API keys, tokens hardcoded in JS or build-time env injection.

Bundle is extractable; move secret-key ops server-side. → plan-secrets-audit

• Plaintext token storage — auth tokens in localStorage, @capacitor/preferences,

IndexedDB, plain SQLite. Wrong. Use memory-only or iOS Keychain / Android Keystore (@capacitor-community/secure-storage, capacitor-secure-storage-plugin, Identity Vault).

• `allowBackup` (Android) — android:allowBackup="true" exfiltrates app data via backups.

2 · Authentication & deep linking

• Custom URL scheme OAuth — myapp:// not globally owned; malicious app can intercept.
• No PKCE — OAuth2 in native apps must use PKCE.
• Custom scheme vs App/Universal Links — prefer Universal Links (iOS) / App Links

(Android) with assetlinks.json / AASA. Note silent verification fallback to browser.

• Exported Android components — exported=true + BROWSABLE + no validation = common

deep-link compromise. Audit every <intent-filter>.

• Deep-link input not validated — URI params → WebView.loadUrl, file access, queries.

startsWith host checks inadequate.

3 · Network security

• Non-HTTPS — any http:// in plaintext.
• `cleartext: true` in capacitor.config — dev/live-reload only; never production.
• Missing `network_security_config` (Android) — usesCleartextTraffic="false"; pinning

for high-assurance (note bypass risks).

4 · WebView security

• No / weak CSP — Content-Security-Policy meta tag scoping loads.
• Broad `allowNavigation` — untrusted hosts load with native bridge attached; scope to

trusted API origin(s). Note getPlatform() quirk on navigated URLs.

• `webContentsDebuggingEnabled: true` in production — remote inspection; gate to dev.
• `addJavascriptInterface` / bridge exposure — untrusted content + JS interface =

Critical RCE vector.

• *`setAllowFileAccess / file://**, eval on user input, insecure postMessage`.

5 · OTA / live-update governance

• Update channel integrity — OTA bundles signed/encrypted; unauthenticated path = RCE.
• Store-policy — Google permits WebView updates; **Apple: OTA must not alter core

functionality** (App Store violation independent of security).

• Rollback / kill switch — can a bad update be reverted?

Severity aligned with Cap-go CAP001–010 / AND001–008 where applicable.

For each finding: location, gap, exposure, severity, remediation direction.

Procedure

1. Inventory. Read capacitor.config.*, AndroidManifest.xml, Info.plist, network

configs, OAuth/deep-link setup, token storage. State what you couldn't see.

1. Run pillars 1–5. Tag Critical (bridge/addJavascriptInterface to untrusted

content, hardcoded signing key, plaintext secrets shipped), High (cleartext, broad allowNavigation, exported component, custom-scheme OAuth w/o PKCE, plaintext tokens), Med (debug flags, allowBackup, weak CSP), Low (logging nits).

1. Config-vs-production table — dev-only settings live in prod build.
2. Phase burndown. Production-config leaks and token storage first.
3. Emit `plan-capacitor-hardening.md`. End the turn.

Guardrails

• Plan only. No config, manifest, or storage migration edits.
• "Works in the browser" hides all of this. Say so explicitly.
• Dev config is a production vulnerability. cleartext, webContentsDebuggingEnabled,

broad allowNavigation must not ship.

• In-memory or hardware-backed only for tokens/keys — not Preferences/localStorage.
• Universal/App Links + PKCE for sensitive OAuth; custom scheme = High even if "works".
• Cross-hand: bundle secrets → plan-secrets-audit; deep-link validation →

plan-input-validation; submission → plan-mobile-readiness.

• Minimal quoting of config/manifest.

Report template — plan-capacitor-hardening.md

# Capacitor Native-Layer Hardening Audit — <app>

_Audit-only. Native security. Nothing changes until each phase is approved._
_These findings are invisible to web-only review._

## Scope
- Inspected: capacitor.config ☐ AndroidManifest ☐ Info.plist ☐ token storage ☐ OAuth ☐ OTA ☐
- Platforms: iOS ☐ Android ☐  | Assumptions: …

## Dev-config-in-production
| Setting | Prod value | Risk | Direction |
|---------|------------|------|-----------|
| server.cleartext | true | plaintext HTTP | false |
| webContentsDebuggingEnabled | true | remote inspection | dev-only |
| server.allowNavigation | ["*"] | bridge on untrusted origin | scope to API |

## Verdict
| Pillar | Crit | High | Med | Worst item |
|--------|------|------|-----|-----------|
| Data | n | n | n | tokens in localStorage |
| Auth/Deep-link | n | n | n | custom-scheme OAuth, no PKCE |
| Network | n | n | n | cleartext enabled |
| WebView | n | n | n | bridge exposed |
| OTA | n | n | n | unsigned channel |

## Findings
| # | Pillar | Location | Gap | Sev | Direction |
|---|--------|----------|-----|-----|-----------|

## Phased burndown
- **Phase 1 — Strip dev config from prod** → `mobile-capacitor-platform`
- **Phase 2 — Secure token storage** → `mobile-capacitor-platform` / `plan-secrets-audit`
- **Phase 3 — Auth & deep-link** → PKCE, App/Universal Links, exported review
- **Phase 4 — WebView & network** → CSP, network_security_config, bridge exposure
- **Phase 5 — OTA governance** → sign channel, store-policy, rollback

## Execution handoff
Re-audit native files after each phase; verify secure storage + deep-links on real devices.

Chains with

• Launch gates — run with plan-mobile-readiness before store submit.
• `plan-secrets-audit` — bundle secrets cross-hand.
• `plan-input-validation` — deep-link / WebView input validation cross-hand.
• Execution: mobile-capacitor-platform, backend-patterns, mobile-emulator-test.
• Verify: real-device secure storage + deep-link test; no dev config in release build.

Plan with a strong model; execute with composer-2.5-execution.mdc.