In the expression “opening Pandora’s box,” what does the phrase usually mean?

In the expression “opening Pandora’s box,” the phrase usually means releasing unforeseen problems.

The idiom comes from the Greek myth in which Pandora opens a container and allows evils to escape into the human world. In modern English, it is used figuratively for an action that begins a chain of harmful, complicated, or difficult consequences that are hard to control afterward.

The phrase does not normally refer to literal curiosity alone. Its key idea is consequence: someone takes an apparently limited step, but that step exposes a much larger set of troubles. Writers use it in discussions of politics, technology, law, science, and personal decisions.

The idiom is also based on the later “box” form of the story. Hesiod’s original vessel was a pithos, or storage jar. Even so, “Pandora’s box” is now the standard English expression, and the figurative meaning is widely understood independently of the ancient details.