Large-scale deployments of web applications occur continuously. The failure to validate or sanitize form inputs, improperly configured web servers, and application design flaws are the main causes of security vulnerabilities that continue to infect web applications, allowing hackers to access sensitive data and using legitimate websites as a breeding ground for malware. These vulnerabilities can be used to compromise the security of the application. The largest problem that enterprises face is how to create a web application that satisfies their needs for safe processes, E-Commerce, and the transmission of sensitive data. OWASP updates and releases a list of the top 10 web application vulnerabilities every few years. Along with the OWASP Top 10 Threats, this chapter also discusses each vulnerability's possible effects and how to avoid them. According to the OWSP (Open Online Application Security Project) Top Ten, this document analyses the most serious web vulnerabilities, their causes, and their impacts.