Improper validation of input is one of the most common and inherent flaws in most web applications.

This weakness further leads to many critical vulnerabilities in web applications, such as cross-site scripting, SQL injection, buffer overflows, and so on.

Most times when an application is developed, it blindly accepts all the data coming to it. However from the security perspective, this is a harmful practice as malicious data could also get in due to lack of proper validation.