What is the common modern meaning of “opening Pandora’s box”?

“Opening Pandora’s box” commonly means starting a chain of troubles.

The expression comes from the myth in which Pandora opens a container and releases evils into the human world. In modern English, it is usually applied figuratively to an action that creates many unexpected problems or consequences. The phrase often implies that the consequences are difficult or impossible to reverse.

The idiom is used in journalism, politics, law, science, and everyday conversation. For example, a decision that resolves one immediate issue but creates several larger disputes may be described as opening Pandora’s box. The expression does not normally refer to a literal container or to the discovery of valuable objects.

A common mix-up concerns the myth’s moral. The idiom stresses danger and trouble, while many retellings also emphasize the survival of hope. The two ideas can coexist: an action may unleash serious problems while leaving some possibility of endurance or recovery.