In application security, we focus on testing several different types of applications: web, mobile and desktop, and it includes API testing as well. In the present digital and electronic times, they form an integral part of us, and we practically use them in our everyday activities. Therefore, their security becomes significant not only for the protection of an organization or a system, but above all for ensuring the protection of sensitive information and data. When testing applications, our aim is to identify vulnerabilities which may compromise their confidentiality, integrity, or availability. In the application security lab, we focus not only on the common attacks exploiting typical vulnerabilities and the protection against them, but also on the latest trends in the secure development - from design, through architecture, all the way to deployment and administration.