This bachelor's thesis addresses the topic of security threats for web applications, with the practical part presenting a security assessment of selected e-learning applications. It describes the most common current threats for web applications, attack techniques and security techniques. The web environment gave rise to a whole range of techniques for breaching the security of web applications, and this thesis therefore presents the most common threats. The second part of the thesis introduces security techniques, both general techniques based on securing the protocol and techniques against specific threats. The protocol on which an application runs is one of the most important security components, and therefore the thesis analyses the func...