To ensure that SecAdmin1 can apply quick fixes to the virtual machines by using Azure Defender, while also following the principle of least privilege, you should assign the Contributor role for RG1 to SecAdmin1. The Contributor role for RG1 will allow SecAdmin1 to perform tasks such as deploying resources and modifying resource properties within RG1, but it will not grant them access to perform administrative tasks at the subscription level. This will allow SecAdmin1 to apply quick fixes to the virtual machines using Azure Defender, while still adhering to the principle of least privilege.