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    JWT Analyzer

    Decode and analyze JSON Web Tokens for security vulnerabilities. Check algorithm safety, expiration, sensitive data exposure, and header injection risks.

    About JWT Security

    Common Vulnerabilities

    • Algorithm None: Attacker removes signature verification
    • Key Confusion: Switching RS256 → HS256 to sign with public key
    • JKU/X5U Injection: Pointing to attacker-controlled key servers
    • Weak Secrets: Brute-forceable HMAC signing keys

    Best Practices

    • Always validate the alg header server-side
    • Set short expiration times with refresh tokens
    • Never store sensitive data in JWT payloads
    • Use asymmetric algorithms (RS256, ES256) when possible

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