What phrase describes an action that causes many unforeseen problems, echoing Pandora’s myth?

“Opening Pandora’s box” describes an action that causes many unforeseen problems.

The expression comes from the myth in which Pandora opens a container and releases evils into the world. In modern English, it is used figuratively when an apparently small decision creates a complicated chain of harmful or difficult consequences.

The phrase usually suggests that the consequences are hard to reverse. It can describe political decisions, technological experiments, legal disputes, or personal choices. It does not normally mean simply discovering a secret; the emphasis is on unleashing troubles that were previously contained.

The expression uses “box,” even though Hesiod’s original object was a pithos, or large jar. That translation history explains why the idiom and the earliest Greek wording do not match exactly. “Opening Pandora’s box” became established in English through later retellings and literary usage.