This analytic rule detects the assignment of the 'full_access_as_app' permission to an application within Office 365 Exchange Online, utilizing Azure Active Directory (AAD) AuditLogs. The rule specifically looks for operations named 'Update application' and identifies the permission assignment through the ResourceAppId '00000002-0000-0ff1-ce00-000000000000' and the EntitlementId 'dc890d15-9560-4a4c-9b7f-a736ec74ec40'. By allowing an application full access as a user, this can pose significant security risks, including unauthorized access to all mailboxes and the capability to send emails on behalf of users. This makes it crucial to monitor and investigate any unexpected permission assignments due to their potential use in data exfiltration or malicious activities.