In modern English, what does opening “Pandora’s box” usually release metaphorically?

In modern English, opening “Pandora’s box” usually means causing unexpected troubles or complications.

The expression comes from the Greek myth in which Pandora opens a sealed vessel and releases destructive forces into the human world. As an idiom, it describes an action that begins a chain of difficult, harmful, or unpredictable consequences. The phrase is used in journalism, politics, law, science, and everyday conversation.

The metaphor does not normally refer to literal evil escaping from a container. It warns that investigating or initiating something may create problems that are difficult to control or reverse. The expression can also suggest that an issue contains many connected complications.

The common English wording says “box,” although Hesiod’s original Greek story describes a pithos, or large storage jar. That translation history explains why the idiom’s modern image differs from the earliest surviving literary version.