Short definition: Reusing a stolen authentication token to impersonate a legitimate user.
1 min read
What it is
Attackers intercept or steal authentication tokens-such as session cookies or JWTs-and reuse them to bypass logins entirely.
Why it matters
Replay attacks grant attackers full access without needing passwords. They are common in API-based systems and mobile apps.
How to reduce risk
- Use HTTPS + HSTS
- Rotate tokens frequently
- Bind tokens to devices
- Invalidate tokens on logout
- Prevent XSS
- Store tokens securely