The growing maturity of orchestration languages, such as the Topology and Orchestration Specification for Cloud Applications (TOSCA) language, and the continuous improvement of virtualization techniques contribute to the large-scale deployment of cloud composite services based on multiple resources that may be hosted over different cloud service providers. The resources composing these services may be subject to migrations, either live or offline, in order to cope with performance objectives, such as load balancing, latency minimization, and energy savings. However, these migrations may induce changes affecting the configurations of migrated resources. In particular, these changes may lead to vulnerabilities, that may compromise the security of resources, or even the security of the whole cloud service. This demonstration showcases a vulnerability prevention tool, called CMSec, for supporting the resource migrations of TOSCA-based cloud composite services by considering OVAL vulnerability descriptions together with verification techniques. Based on two main scenarios, we will expose how the CMSec tool is able to detect vulnerable configurations prior to resource migrations, and to suggest corrective operations for remediating them.