Re: At least a software that will block Postel famous principle...
Indeed. What this really means, is that the output of your code should be well define and meet the specification (conservative in what you do), but should handle unexpected input with an appropriate response (be liberal in what you accept).
In practise, that means responding with an appropriate error, rather than assuming the input was correct and continuing anyway. In effect you shouldn't trust any data that you didn't create yourself (and because no software is ever 100% bug free*, you probably shouldn't trust your own data either until you've validated it).
For example, if you have a web service with an API endpoint that is expecting some well formed JSON, and the consumer posts a gif of a dancing monkey to it instead, it should return a 400 response, and try to deserialise the monkey and carry on like it was all fine. Otherwise, such handling of unexpected input could result in an unpredictable error later on in your process, and potentially result in an exploitable vulnerability, such as a buffer overflow, or SQL injection attack.
In other words, the Postel principle could be read as "expect other systems to pass all sorts of crap to you, and handle it appropriately." Appropriately, in almost all cases, being to reply with "unexpected input" or similar. After all, if the input is outside of what has been specified, then the behaviour that should be exhibited is also unspecified.