One possible moral could be about the consequences of greed. In the Jack and Beanstalk story, Jack's actions of trading the family cow for magic beans and then climbing the beanstalk to take from the giant could be seen as driven by greed. And he has to face the dangerous giant as a result.
The moral might also be about taking risks and facing the unknown. Jack takes a huge risk by climbing the beanstalk into an unknown world. It shows that sometimes in life, we need to step out of our comfort zones but also be prepared for the challenges that come with it. He encounters a giant, which is a big challenge, but through his wits, he manages to survive and come back with treasures. So it's about weighing the risks and rewards.