can of worms

any situation that creates more problems than existed beforehand

The Can of Worms is a local name for the intersection of Interstates 590 and 490 on the east side of Rochester, New York. Since the intersection was rebuilt from 1988 to 1991, the name has fallen into disuse, but from the time of its construction until then it was a major source of comment locally for its effect on traffic.
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Noun
1. a source of unpredictable trouble and complexity
(hypernym) trouble, problem
(classification) colloquialism

complex problem or complicated situation It opened up a large can of worms when the company decided to talk about the union contract.

IMBROGLIO. PASTICCIO