If a Struts Action Form Mapping specifies a form, it must have a validation form defined under the Struts Validator. If an action form mapping does not have a validation form defined, it may be vulnerable to a number of attacks that rely on unchecked input. Unchecked input is the root cause of some of today's worst and most common software security problems. Cross-site scripting, SQL injection, and process control vulnerabilities all stem from incomplete or absent input validation. Although J2EE applications are not generally susceptible to memory corruption attacks, if a J2EE application interfaces with native code that does not perform array bounds checking, an attacker may be able to use an input validation mistake in the J2EE application to launch a buffer overflow attack. An action or a form may perform validation in other ways, but the Struts Validator provides an excellent way to verify that all input receives at least a basic level of checking. Without this approach, it is difficult, and often impossible, to establish with a high level of confidence that all input is validated.