Is mandatory data validation required only for POST requests?

Mandatory data validation is necessary not only for POST requests but also for any other types of requests that accept data from the user (for example, PUT, PATCH, DELETE, and sometimes GET with parameters). Data validation ensures the security and correct operation of the application, preventing errors and attacks (such as SQL injections, XSS). Even if data comes in the body of a POST request, it is important to validate it by type, format, and content before use.