# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-M365-APPS-013
title: Remove unsafe redirect URIs from applications
finding:
  title: Applications accept redirect URIs that an attacker could control
  description: Wildcard, plain HTTP or abandoned redirect URIs let an attacker receive authorization codes and tokens issued for a legitimate application.
status: active
profiles: [hardened]
risk:
  severity: medium
assessment: manual
tags: [applications, oauth, redirect-uri, token-theft]

description: |
  Redirect URIs (reply URLs) of application registrations are restricted to addresses the
  organization controls:

  - no wildcard (`*`) in a URI;
  - `https` only, except `http://localhost` for native and development clients;
  - no URI on a domain the organization no longer owns or that is not registered (for example an
    expired domain, a deleted `azurewebsites.net` or `cloudapp.net` host, a third-party URL
    shortener);
  - no URI left over from tests (`https://jwt.ms`, `https://oauth.pstmn.io`, personal
    `ngrok` hosts) on production applications.
rationale: |
  Microsoft Entra sends authorization codes and, for implicit flows, tokens to the redirect URI. If
  that URI points to a host an attacker can register or intercept, the attacker receives the
  victim's code for a trusted application and can redeem it. Dangling cloud host names are claimed
  by attackers precisely for this purpose.
impact: |
  Removing a URI still used by a client breaks sign-in for that client. Confirm with the
  application owner first.

audit:
  manual: |
    1. Sign in to the Microsoft Entra admin center (https://entra.microsoft.com) as at least a
       Global Reader.
    2. Browse to **Entra ID** > **App registrations** > **All applications**, open each application
       and review **Authentication** > **Platform configurations** (Web, Single-page application,
       Mobile and desktop).
    3. In Microsoft Graph PowerShell (scope `Application.Read.All`), list URIs with
       `Get-MgApplication -All -Property displayName,appId,web,spa,publicClient | Select-Object displayName,@{n='uris';e={$_.Web.RedirectUris + $_.Spa.RedirectUris + $_.PublicClient.RedirectUris}}`.
    4. Resolve each host name: check it is a domain the organization owns and that the DNS name
       still points to a resource the organization controls.
    5. Fail if any URI contains a wildcard, uses `http` to a host other than `localhost`, points to
       an unregistered or third-party-controlled host, or is a test URI on a production
       application.

remediation:
  manual: |
    1. With the application owner, list the redirect URIs actually used by the clients.
    2. Browse to **App registrations** > the application > **Authentication** and delete the unsafe
       URIs, or replace them with exact `https` URIs on domains you control.
    3. Graph alternative: `Update-MgApplication -ApplicationId <id> -Web @{ RedirectUris = @('<uri>') }`.
    4. Remove dangling DNS records that pointed to deleted cloud resources.
    5. Role required: Cloud Application Administrator, or owner of the application.
  rollback: |
    Add the removed URI back under **Authentication** once its host is confirmed to be under your
    control.

references:
  - title: Redirect URI (reply URL) best practices and limitations
    url: https://learn.microsoft.com/entra/identity-platform/reply-url
    publisher: Microsoft
    kind: vendor-doc
    accessed: 2026-10-24
mappings:
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-6
    relation: related
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: AC-3
    relation: related
threats:
  - framework: mitre-attack
    id: T1528
related_controls:
  - id: CB-M365-APPS-019
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
introduced_in: 0.1.0
created: 2026-10-24
updated: 2026-10-24