can of worms

to reveal a problem or to create additional problems by revealing information.

The hacked account was only the tip of the iceberg, and further investigations opened up a can of worms.

Tigers pitchers, including Jose Valverde, rocked by Orioles
The uncertain can of worms that has been open ever since Jose Valverde returned to the Tigers was pried apart even wider in a 13-3 loss to the Baltimore Orioles on Wednesday.
June 19, 2013 - Detroit News
An athlete is an athlete
Former Super Bowl-winning quarterback Joe Theismann has never been known to run out of things to say. He has always been quick to offer up his opinions on today's NFL and last week, he made no exception. What started off as a bizarre statement about LeBron James, opened up a huge can of worms and sparked an NFL vs. NBA debate.
June 18, 2013 - Gonzales Weekly Citizen
An athlete is an athlete
Former Super Bowl-winning quarterback Joe Theismann has never been known to run out of things to say. He has always been quick to offer up his opinions on today's NFL and last week, he made no exception. What started off as a bizarre statement about LeBron James, opened up a huge can of worms and sparked an NFL vs. NBA debate.
June 18, 2013 - Gonzales Weekly Citizen

can of worms : Popular Idioms in English