The phrase "major leak" refers to a significant or large-scale release of confidential or secretive information, typically causing serious consequences or a loss of trust. Full definition
I call the insurance guy out and he finds buckets sitting on towels in the attic from where the previous owner was trying to hide major leaks in the roof. (massrealestatenews.com)
I have had a few experiences with major leaks, but I can attribute that to my toddler holding it in for a long time and then letting the flood gates open. (the-cloth-diaper-connection.com)
He also looks at jobs placed at risk when spills or major leaks occur. (policynote.ca)