Code security is a crucial element of the SDLC (Software Development Life Cycle). Bugs exist because we are human. However, by examining various vulnerabilities and incidents that have occurred in the past, one can prevent harm from happening. Below you will find an eBook that will be continuously updated. It discusses code and web security, exploring several vulnerabilities with practical examples which can be found in my GitHub repository at https://github.com/mouadk/application-security.