AWS EC2 Transit Gateways automatically accept VPC attachment requests

Description

A transit gateway enables you to attach VPCs and VPN connections in the same Region and route traffic between them. Make sure to specify one subnet from each Availability Zone to be used by the transit gateway to route traffic. Specifying one subnet from an Availability Zone enables traffic to reach resources in every subnet in that Availability Zone. Enabling 'accepting shared attachments' automatically accept cross-account attachments.