Create and assign the Field Service Guest User permission set to provide permissions for unauthenticated users to run appointment booking and scheduling actions. Salesforce is improving guest user security, and this new permission set helps you adhere to the security requirements for guest users.
Where: This feature is available in Lightning Experience in Enterprise, Unlimited, and Developer editions with the Field Service managed package installed.
When: Starting in Spring ’22, you can no longer assign guest users permission sets or permission set groups associated with permission set licenses that contain View All, Modify All, Edit, and Delete standard object permissions. In Winter ’23, Salesforce enforces this update and removes the affected permission set and permission set group assignments from guest users. If you’re affected, Salesforce Customer Support contacts you directly about your process and timeframe for the update.
How: In the Field Service Admin app, Field Service Settings tab, click Getting Started, and then click Permission Sets. On the Field Service Guest User tile, click Create Permissions or Update Permissions.
Tighten Security for Unauthenticated Guest User Scenarios (salesforce.com)