Definition: a prolific source of troubles
The god Prometheus stole fire from heaven to give to the human race, which originally consisted only of men. To punish humanity, the other gods created the first woman, the beautiful Pandora. As a gift, Zeus gave her a box, which she was told never to open. However, as soon as he was out of sight she took off the lid, and out swarmed all the troubles of the world, never to be recaptured. Only Hope was left in the box, stuck under the lid. Anything that looks ordinary but may produce unpredictable harmful results can thus be called a Pandora's box.
A modern twist on the Greek inspired idiom
Metaphorically speaking, to open a can of worms is to examine or attempt to solve some problem, only to inadvertently complicate it and create even more trouble. Literally speaking, opening a can of worms, as most fishermen can attest, can also mean more trouble than you bargained for. (Mental Floss)
Dulcis in fundo (last but not least)
- a situation in which effort to solve a given problem results in aggravation of the problem or the creation of a worse problem: