can of worms

American  

noun

1. Informal. a source of many unpredictable or unexpected problems.

   Buying a company we know nothing about would be opening up a whole new can of worms.

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can of worms Idioms  

1. A complex unexpected problem or unsolvable dilemma, as in Tackling the budget cuts is sure to open a can of worms. This expression alludes to a container of bait used for fishing, which when opened reveals an inextricable tangle of worms. [1920s]

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Etymology

Origin of can of worms

First recorded in 1965–70

Example Sentences

“It opens up a whole new can of worms.”

From The Wall Street Journal

What remains to be seen now is whether a wider can of worms has been opened.

From BBC

“China is reopening the same can of worms.”

From The Wall Street Journal

Nudleman prefers to use his Amazon Fire Stick’s voice search feature to look for specific titles he’s interested in, but that experience is its own can of worms.

From Salon

Another little disagreement on their way to a Tokyo market the next day opened up “a can of worms,” she said.

From Los Angeles Times