Why It’s Important

Password reset is the highest-risk feature of your authentication stack. It is literally a way to bypass login — and if you get it wrong, you could hand over accounts to attackers.

Common mistakes include:
✅ reusing predictable reset tokens
✅ forgetting token expiration
✅ leaking reset tokens in URLs
✅ failing to invalidate used tokens
✅ not rotating session secrets

We’ll build a secure, production-grade password reset that avoids these traps.

1. High-Level Password Reset Flow

✅ User initiates reset (supply their email)
✅ Backend issues a cryptographically random token stored hashed in the DB
✅ Send a one-time link with the token to the user’s email
✅ User clicks link → new password form
✅ Backend verifies token (one-time, with expiry)
✅ Reset password + kill all other sessions

2. Sample Django Implementation (concept applies to any backend)

Let’s show real code with Django:

When user requests a reset:

✅ Note: store only a hashed version of the token
✅ Never reveal whether the email is registered
✅ Token expires in 1 hour

When user clicks the link:

✅ Validate token securely with constant-time comparison
✅ Expire the token after use
✅ Flush all sessions after a password change

3. Security Best Practices Checklist

✅ Hash tokens in DB (make_password)
✅ Generate long random tokens (>=64 chars, cryptographically secure)
✅ Expire tokens (1 hour or less is best)
✅ Never reveal user existence
✅ Kill all active sessions after reset
✅ Use HTTPS only
✅ Rate-limit reset requests
✅ Log unusual resets for fraud detection

Common Mistakes

🚫 Using simple UUIDs as reset tokens (easily guessable with enough tries)
🚫 Leaving tokens in query strings for days (they can be leaked via browser history or referer headers)
🚫 Storing tokens in plaintext in your DB
🚫 Allowing unlimited resets without rate limiting
🚫 Failing to rotate user sessions after reset

Bonus: Links Without Query Strings

Many engineers get nervous about tokens in query strings. Modern best practice is to move them to the fragment (#) or to a one-time code entry page. But the most common is a standard reset/<token> pattern because:

• It’s link-click friendly

• Token is ephemeral

• HTTPS protects it

If you worry about logs leaking query params, then avoid query strings, and embed token in the path.

Test Your Flow

✅ Confirm token cannot be reused
✅ Confirm expired token rejection
✅ Confirm correct user password updates
✅ Confirm other sessions die after reset
✅ Confirm no user enumeration is possible

Automated tests should cover these scenarios with tools like Django’s TestCase.

Conclusion

A password reset is a door directly into an account — treat it as a high-value target.
By hashing your tokens, using cryptographic randomness, time-based expiration, and session rotation, you protect users while keeping your system trustworthy.