Understanding Authentication bypass
What it is
Authentication proves who is making a request. A bypass is any path that reaches an authenticated state without presenting the secret that state is meant to require — a default credential, a flawed comparison, a token that is trusted when it should not be, a step in a flow that can be skipped.
How you approach it
- Look at exactly what the login flow checks, and in what order. Is there a state it can be nudged into that skips the check?
- Compare the requests for a failed login and a successful one. What single field decides which you get?
- The gate trusts a value it should have verified. Supply the value it wants, not the credential it asks for.
How it gets fixed
The server decided you were signed in from a value the client controlled rather than one only a real login could produce. Setting that value directly walked past the credential check entirely. The fix is to derive the authenticated state from a server-side session, never from a request the client can forge.
Practise it
Every lab in the Authentication bypass category drills exactly this. Start at Apprentice and work up.