The point: Attackers can use OAuth client ID spoofing to enumerate Microsoft Entra user accounts and validate credentials without classic sign-in attempts being logged.
At least two threat actors are using an evasion technique called OAuth client ID spoofing in cloud attacks to validate stolen credentials against Microsoft Entra ID without triggering sign-in events that would alert Defender.
The technique exploits a vulnerability in credential validation: attackers validate stolen login credentials against Microsoft Entra ID without generating a successful or failed sign-in event that would normally be visible in telemetry systems. This enables the identification of user accounts and testing of credentials while the typical detection channels (failed sign-in attempts, suspicious sign-in patterns) remain silent.
The approach is particularly dangerous because Defender relies on such standard indicators: frequent authentication failures, suspicious sign-in sources, or unusual device profiles. When these signals are absent, the activity is not recognized as an attack — the credentials are validated and ready for an actual breach before the defensive systems can react.
As a CISO, this means: traditional telemetry based on sign-ins is not sufficient. Required are advanced control mechanisms such as Conditional Access, risk-based authentication, and API-level monitoring to capture OAuth flows and client ID anomalies — before an actual sign-in even takes place.
Source: thehackernews.com · Published July 14, 2026
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