Exception:

System.SecurityException: Required permissions are not enabled.

Resolution:

Exception “System.SecurityException: Required permissions are not enabled.” is thrown if the running user doesn’t have the required permission to perform the operations.

For example,

1. To execute Anonymous Apex code, the users need “Author Apex” permission.
2. To send Email from Lead or Contact, the user needs “Send Email” permission.
3. To send Email from Apex, Author Apex permission is required.