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CQURE Hacks #82: Microsoft Entra ID Conditional Access Bypass via User-Agent Policy Gap
Conditional Access decides which device platforms it trusts based on the User-Agent, a value the client controls. Windows, Linux, iPhone all get blocked. So, we try something the policy never accounted for: Xbox Series X. The result is a Microsoft Graph access token, issued without ever triggering MFA.
With that token we go straight to Graph, enumerating users, groups and roles with GraphRunner, completely bypassing the portal restrictions. A custom script then scans directory objects for secrets and finds a clear-text password sitting in a group description. It belongs to a break-glass account with Global Administrator.
One policy gap and one badly stored secret, chained into a full tenant compromise.
Blocking the admin portal is not enough. Conditional Access has to cover the underlying APIs and token acquisition paths, security decisions must not rely on client-controlled signals like the User-Agent, MFA belongs on every sensitive path, and secrets must never live in directory attributes a standard user can read.
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The post CQURE Hacks #82: Microsoft Entra ID Conditional Access Bypass via User-Agent Policy Gap appeared first on CQURE Academy.
