AWS Lambda Permissions give an AWS service or account permission to use a function. Not configuring the source ARN for the lambda function permissions could allow unintended access. It is considered best practice to specify the source ARN in cloud services.
In AWS Console -
In Terraform -
References:
https://docs.aws.amazon.com/lambda/latest/dg/security-iam.html
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-lambda-permission.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/lambda_permission