What phrase describes releasing many hidden problems by starting one seemingly simple action?

The phrase “opening Pandora’s box” describes releasing many hidden problems through one seemingly simple action.

The expression comes from the Greek myth in which Pandora opens a sealed vessel and harmful forces escape into the world. In modern English, the phrase is usually figurative rather than literal. It warns that investigating, changing, or revealing something may produce a chain of difficult consequences that cannot easily be reversed.

People often use the expression for politics, technology, legal disputes, or personal conflicts. It does not necessarily mean that every consequence was deliberately caused; the emphasis is on consequences that multiply after an initial step.

The standard English wording is “open Pandora’s box” or “opening Pandora’s box.” The original Greek story involved a jar or storage vessel, not the familiar modern box, because “box” became established through later translation and retelling.