Testing non-functional properties like security, reliability, or even resilience has gained a lot of attention recently. In my talk, I focus on security and there in particular on providing testing methodologies that can be used to detect known vulnerabilities in order to avoid making mistakes twice. Techniques and methods, I discuss including planning-based and ontology-based testing make use of methods originating from artificial intelligence to create test cases for detecting security issues. Besides providing the foundations behind those methods, I also report on most recent experimental results obtained when using these methods for detecting vulnerabilities regarding injection and cross-side scripting. In addition, we discuss open issues and current research topics in security testing.