What expression describes releasing many unexpected problems by opening Pandora’s box?

The expression “opening Pandora’s box” describes releasing many unexpected problems. It comes directly from the myth in which opening a container allows evils or troubles to spread into the human world.

In modern English, the phrase is usually used figuratively for an action that begins a chain of difficult, harmful, or uncontrollable consequences. It can apply to politics, technology, law, personal decisions, or any situation where an apparently small step creates wider complications.

The wording is based on the later “box” tradition, even though Hesiod’s original container was a jar. It is also commonly confused with “Pandora’s box” as the name of the object itself. “Opening Pandora’s box” is the action-based idiom, while “Pandora’s box” can refer either to the mythic container or to a source of problems.