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Ottergram (BAC + HTTP Verb Tampering) — Bugforge

EN medium CTF challenge BACBroken Access ControlHTTP Verb TamperingIDORAuthorization BypassBurp Suite
Original

Ottergram is a social-media-style web application on Bugforge.io where users browse otter photos. The attack chain is two-stage: first, find functionality you shouldn't be able to reach. Then, find a way past the gate that's supposed to stop you.

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resueltos
Paso 1 Paso 2 Paso 3 Paso 4 Paso 5
web

Paso 3 · Attempt Direct Access — Confirm BAC Surface

Objetivo: Confirm that the access control check on the admin endpoint is enforced but potentially bypassable, by sending the blocked request through Burp Suite with your regular-user session token.

Contexto: You have identified an admin endpoint. Your regular-user session cookie/token is available in Burp Suite. The server currently returns 403 for this endpoint.

Pistas progresivas

Revela solo las que necesites. Claude lleva la cuenta de cuántas usaste para calibrar la retroalimentación.

Pista 1 — empujón direccional

Send the blocked request to Burp Repeater and replay it with your own session. Observe exactly what the server returns — note the HTTP status code and response body.

Pista 2 — técnica / clase de vuln

Access control can sometimes be enforced at the routing/middleware layer rather than the endpoint logic layer. Consider whether changing something about the *request itself* — not the credentials — might bypass the check.

Pista 3 — casi la solución

The access control may be enforced only for specific HTTP methods (e.g., GET or POST). Try sending the same request but with a different HTTP verb — such as PUT, PATCH, HEAD, or OPTIONS — to the same admin endpoint in Burp Repeater.

Pregúntale al tutor

Chatea con un tutor anti-spoiler para este paso. Usa solo la especificación de este lab y empieza por la pista más pequeña que sirva.

Cuéntale qué probaste, dónde te atoraste, o pega la respuesta/error que estás viendo.

Tu intento

¿Encontraste algo para mejorar?

Puliendo la redacción, afinando una pista, agregando contexto que falta, corrigiendo un payload — tu versión queda separada de la original y otros aprendices pueden elegirla.

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