Project: WASC Threat Classification

Threat Type: Weakness

Reference ID: WASC-20


Improper Input Handling


Improper input handling is one of the most common weaknesses identified across applications today. Poorly handled input is a leading cause behind critical vulnerabilities that exist in systems and applications.


Generally, the term input handing is used to describe functions like validation, sanitization, filtering, encoding and/or decoding of input data. Applications receive input from various sources including human users, software agents (browsers), and network/peripheral devices to name a few. In the case of web applications, input can be transferred in various formats (name value pairs, JSON, SOAP, etc…) and obtained via URL query strings, POST data, HTTP headers, Cookies, etc… Non-web application input can be obtained via application variables, environment variables, the registry, configuration files, etc… Regardless of the data format or source/location of the input, all input should be considered untrusted and potentially malicious. Applications which process untrusted input may become vulnerable to attacks such as Buffer Overflows, SQL Injection, OS Commanding, Denial of Service just to name a few.