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IDOR: the simple bug that keeps paying off

Notes on why insecure direct object references are still everywhere, and a repeatable way to hunt for them in modern apps.

May 20, 20259 min read

Still here

Insecure direct object references are not glamorous, but they remain one of the most common high-impact findings in web assessments. Modern frameworks make injection harder; they do almost nothing for authorisation.

A repeatable hunt

Map every object the app exposes, note the identifier each uses, then replay requests as a second user. Sequential identifiers are a gift, but even opaque ones fall when the server never checks ownership.

The fix

Authorise every object access on the server, keyed to the authenticated user, not to what the client sends. It sounds obvious and it is still the single most common gap I report.

  • #web
  • #access-control
  • #methodology