"Pandora's box"

Pandora is a character in Greek mythology.  In the story, she is a woman living shortly after the world was created, who is given a large sealed jar (or box) by Zeus, king of the Gods, and told never to open it.  Curiosity gets the better of her and she does open the box, releasing all the evils of the world (e.g., disease and hard work) which were trapped inside.