Just like one can have safe_parse() and unsafe_parse(), there could be an elevated API that could be safely used when vetted. For instance, when the SMTP server

Just like one can have safe_parse() and unsafe_parse(), there could be an elevated API that could be safely used when vetted. For instance, when the SMTP server rejects a request it could put it in a special queue which requires manual confirmation. This type of problems happen so regularly. In fact, a Japanese trader accidentally punched one too many zeros and lost a lot of money for the company. This type of problems can get very expensive in an instant. As an industry, we tend to think of input validation in passing because we don't pay enough attention to the problem domain.