Login Access Policy Changed

Administrators with “Modify All Data” permission and delegated administrators with “View Setup and Configuration” permission can log in as any user without asking end users to grant access. The Administrators Can Log in as Any User setting on the Setup | Security Controls | Login Access Policies page is available by default. Previously, this option was only available when organizations explicitly requested it from Salesforce.
Available in: Enterprise, Performance, Unlimited, and Developer Editions

If you don’t want the Administrators Can Log in as Any User setting to be available for your organization, contact Salesforce to remove it.

If Salesforce removes the Administrators Can Log in as Any User feature from your organization, a user must grant login access before an administrator can log in to that user’s account for troubleshooting. For the steps a user takes to grant access, see Grant Login Access.