Mobile App Security Best Practices in 2026

A developer outlines mobile app security best practices for React Native and Expo apps in 2026, focusing on the OWASP Mobile Top 10. Key recommendations include using expo-secure-store instead of AsyncStorage for tokens, implementing PKCE for OAuth, certificate pinning, and runtime checks for jailbroken devices. The guide emphasizes automated security scanning with tools like Semgrep and MobSF, and advises against trusting any external input.

AsyncStorage . expo-secure-store , never AsyncStorage . Period. semgrep + eslint-plugin-security + npm audit + MobSF on every release artifact.Mobile attacks are up. Regulators are watching. AI is writing more of your code than ever — and the patterns it reproduces aren't always the secure ones. Here's the practical checklist I run through for every React Native / Expo app, organized around the OWASP Mobile Top 10 2024 . This is the working version of a longer guide — focused on what to actually change in your codebase this week. // ❌ Don't await AsyncStorage.setItem 'access token', token ; // ✅ Do import as SecureStore from 'expo-secure-store'; await SecureStore.setItemAsync 'access token', token, { keychainAccessible: SecureStore.WHEN UNLOCKED THIS DEVICE ONLY, } ; Anything in the bundle can be extracted with apktool in minutes. Anything in AsyncStorage is plaintext on disk. Tokens go in the OS keychain via expo-secure-store or react-native-keychain . Period. Refresh tokens rotate on every use. Access tokens live 15 minutes. The backend is the trust boundary, not the client. In CI, on every PR npm ci npm audit --audit-level=high A clean package.json doesn't mean a clean app. Post-install scripts run with your dev-machine privileges. Native modules run with full app privileges. npm ci in CI, never npm install . import as AuthSession from 'expo-auth-session'; // PKCE is the default in expo-auth-session — don't disable it. const request = new AuthSession.AuthRequest { clientId, scopes: 'openid', 'profile' , usePKCE: true, redirectUri, } ; OAuth 2.0 with PKCE for third-party identity. JWTs with 15-minute access tokens and rotated refresh tokens. Every endpoint validates the caller server-side. Hiding UI is not authorization. Add MFA via expo-local-authentication for anything touching payments, identity, or health data. js // Treat the URL params as hostile const handleDeepLink = url: string = { const parsed = new URL url ; const action = parsed.searchParams.get 'action' ; if action && /^ a-z {1,32}$/.test action && KNOWN ACTIONS.has action { routeTo action ; } }; Deeplinks, push payloads, clipboard, QR codes, WebView messages — all untrusted. Validate type, length, format. Parameterized queries for local SQLite. originWhitelist on every WebView . php < -- android/app/src/main/res/xml/network security config.xml -- <network-security-config <domain-config cleartextTrafficPermitted="false" <domain includeSubdomains="true" api.yourapp.com</domain <pin-set <pin digest="SHA-256" {base64-spki-hash}</pin <pin digest="SHA-256" {backup-spki-hash}</pin </pin-set </domain-config </network-security-config Pin to the SPKI hash, not the leaf cert. Ship a backup pin. Have a rotation plan. Reject TLS 1.0/1.1 server-side. In Expo, usesCleartextTraffic: false . Verify no allowsArbitraryLoads snuck into production. Maintain a data inventory. Apply data minimization. Request permissions just-in-time with context. Build account-delete-and-export flows that actually delete and export. Audit analytics/ad SDKs quarterly — they change practices on their schedule. babel-plugin-transform-remove-console in release builds. jail-monkey for rooted/jailbroken detection signal, not block . DEV guards on every debug code path. android:exported="true" only when truly needed.| Sensitivity | Storage | |---|---| | Credentials, keys | iOS Keychain / Android Keystore via expo-secure-store | | Structured PII | SQLCipher or encrypted Realm | | Non-sensitive | Regular filesystem or AsyncStorage | Disable backup for sensitive paths. Mask app-switcher screenshots on sensitive screens via expo-screen-capture . js import { randomBytes } from 'react-native-quick-crypto'; // AES-256-GCM. Never CBC without auth. Never ECB. Ever. Argon2id for password hashing. HKDF for key derivation. SHA-1 and MD5 are dead. Start tracking your post-quantum migration — NIST's ML-KEM and ML-DSA are finalized. This is the one most security frameworks haven't caught up to. LLMs reproduce the most common pattern in their training data — often the most common flawed pattern. .cursorrules or .github/copilot-instructions.md with your secure defaults. semgrep and eslint-plugin-security on AI output before merge.Every PR: semgrep , eslint-plugin-security , Android Lint npm audit + Socket/SnykAnnually: pen test. Quarterly: SDK audit. Always: an incident response plan that includes key rotation, token revocation, and an OTA push. Most mobile breaches aren't sophisticated. They're a hardcoded key, a forgotten debug flag, a plaintext token. The OWASP Top 10 is your checklist — work it every release. For the longer breakdown — including the AI-safe-code generation patterns and the full OWASP-mapped CI workflow — see the RapidNative blog https://www.rapidnative.com/blogs?utm source=devto&utm medium=blog&utm campaign=mobile-app-security-2026 . What's the security gotcha you've shipped to production and then quietly patched? Drop it in the comments — I'm collecting the failure modes that don't make it into the OWASP examples for a follow-up.