You’re told that SSO is the most secure option. A single, fortified gate for all your applications.

It turns out that the gate can sometimes be held open with a simple piece of string.

During a recent engagement, a common SSO misconfiguration was identified that could result in a complete account takeover. It’s a simple oversight in how identity providers handle email verification. Let’s break down how this authorization bypass works.

Why This SSO Security Hole Matters

This isn’t a complex attack. It’s a logic flaw.

When this vulnerability is present, a user from one company can access data from another company. All that’s needed is the same email address. The impact is significant and immediate.

The Core Misconfiguration Explained

In a standard SSO flow, an application trusts the identity provider (like Okta or Auth0) to say, “This person is who they say they are.”

The problem is that some providers can be configured to skip a crucial step: verifying that the user actually owns the email address for the application they are trying to access.

How the Authorization Bypass Was Exploited