OAuth Client ID Spoofing Lets Attackers Validate Stolen Microsoft Entra Credentials
Jul 14, 2026
Cloud Security / Identity Security
At least two distinct threat actors are weaponizing a novel evasion technique called OAuth client ID spoofing in cloud campaigns, while slipping past telemetry. The activity allows users to enumerate user accounts and validate stolen credentials in Microsoft Entra ID environments, without ever generating a successful sign-in event that would otherwise alert defenders. And bad actors have begun to exploit this gap to obtain unauthorized access to an organization's cloud services. "A blind spot in cloud sign-in telemetry: Entra ID returns different error responses depending on whether a supplied OAuth client ID is valid," Proofpoint said in a statement. "Attackers exploit this to infer valid usernames and correct passwords at scale, effectively checking stolen credential lists without logging a successful login." In other words, the attacks leverage the OAuth client ID, a globally unique identifier (GUID) assigned to applications when requesting access to ...
