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2026-07-05

Exploiting an API endpoint using documentation

PortSwiggerlabapi-testingwalkthrough

Objective

To solve the lab, find the exposed API documentation and delete carlos. You can log in to your own account using the following credentials: wiener:peter.

Why This Works (The Principle)

  • >The vulnerability: API documentation is often publicly available, particularly if the API is intended for use by external developers. If this is the case, always start your recon by reviewing the documentation..
  • >Root cause: API documentation may or may not be openly available, we may still be able to access it by browsing applications that use the API.
  • >Exploitation: Burp Scanner can be used to crawl the API. We can also browse applications manually using browser.
  • >Key insight: We can interact with API's in ways the developers didn't think

Blind Attempt (15-20 min max)

  • >What I tried: Scoured the application and found that changing the email
  • >Where I got stuck:

Hint Usage (if needed)

  • > Used lab hint
  • > Watched first 30s of video solution
  • >Resume blind with new clue. Still stuck?

Solution Reconstruction

After viewing full solution, close it immediately.

  • > Step 1:
    Expand
    Burp Proxy history showing the web app making its own calls to the /api endpoint
  • > Step 2:
    Expand
    The exposed API documentation page served at /api, listing every available endpoint
  • > Step 3:
    Expand
    The DELETE request sent from the exposed API docs that removes the user carlos
  • > Final payload / exploit:

Key Takeaway

Search for exposed API docs as they might expose all and everything possible to do with API.

Next-Day Blind Replay

  • > Solved entirely from memory
  • > Needed to look at: (write the specific step forgotten)
Lab recall3 blanks

The app calls its own API docs at . Opening that path in a browser lists every endpoint, and a request against the users path removes .

try it before revealing

Read next

  • 2026-07-08 · LabsServer side parameter pollution in query string
  • 2026-07-07 · LabsExploiting server-side parameter pollution in a REST URL
  • 2026-07-07 · LabsExploiting a mass assignment vulnerability
  • 2026-07-06 · LabsFinding and exploiting an unused API endpoint

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Suhesh Kasti — AppSec & Offensive Security

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