All You Need is Guest: Beyond Enumeration

Presented at BSidesLV 2023, Aug. 8, 2023, 5 p.m. (45 minutes)

Azure AD guest accounts are widely used to grant external parties limited access to enterprise resources, with the assumption that these accounts pose little security risk. As you're about to see, this assumption is dangerously wrong. In this talk, we will show how guests can leverage undocumented APIs to bypass limitations and gain unauthorized access to sensitive business data and capabilities including corporate SQL servers, SharePoint sites, and KeyVault secrets. Furthermore, we will reveal how guests can create and control internal business applications to move laterally within the organization. All capabilities presented in the talk work will be demonstrated with the default Office 365 and Azure AD configuration. Next, we will drop PowerGuest, a powerful tool designed to uncover the true scope of guest access in your tenant. PowerGuest can automate limitation bypass, enumerate and dump all accessible data, and allow for interactive non-read actions by the researcher. Finally, we will make up for shattering the illusion of guests having limited access by sharing concrete steps to harden your Azure AD and Office 365 configurations to prevent such attacks and suggest detection logic to catch them if a change in configuration is not possible.


  • Michael Bargury
    Michael Bargury is a security researcher passionate about all things related to cloud, SaaS and low-code security, and spends his time finding ways they could go wrong. He is the Co-Founder and CTO of Zenity, where he helps companies secure their low-code/no-code apps. In the past, he headed security product efforts at Azure focused on IoT, APIs and IaC. He also leads the OWASP low-code security project and writes about it on DarkReading. Michael is a regular speaker at RSAC, OWASP, BSides and DEFCON.


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