🔐 2FA Security Test Cases & Explanations

1️⃣ Check Weak OTPs (000000 - 123456)

• 🔍 Try common predictable OTPs like 000000, 123456, 111111.
• ❗ If accepted, it’s a weak implementation.
• ✅ Should reject these unless correct.

2️⃣ Check null or Empty OTP

• 🧪 Send an empty or null OTP in the API.
• 💥 Some systems mishandle nulls and skip validation.
• ✅ Should return an error, not allow access.

3️⃣ Reuse Previous OTP 🔁

• ⚠️ OTP should be one-time only.
• 🔄 Try resending a previously used valid OTP.
• ❗ If login succeeds again → vulnerability!

4️⃣ Reuse OTP from Another Account 👥

• 🔐 OTP must be tied to a specific user.
• 🧪 Use OTP from Account A to log into Account B.
• ❗ If it works, the system doesn’t bind OTPs correctly.