Okay, but that’s not what was being asked. OP, someone who presumably understands the difference between a totally invalid cert and an expired one, was asking specifically whether clicking through the latter is dangerous.
"Visitors to the site are vulnerable to Man in the Middle (MitM) attacks, IF they click past the warning". I think it's true when there is a man in the middle.
"Visitors to the site are vulnerable to Man in the Middle (MitM) attacks, IF they click past the warning". I think it's true when there is a man in the middle.