I think it's very important to continue to consider the examples and the definition in light of the chapeau. The test in the definition is actually included in the chapeau, so therefore “an activity that undermines the security of Canada” is an activity that undermines the sovereignty, security, or territorial integrity of Canada, or the lives or the security of the people of Canada. The chapeau is meant to raise the bar on the seriousness of the actions. Therefore any interference with the economic or financial stability of Canada needs to be read with the chapeau in mind. It has to reach that scope that affects the country in a national way. Therefore we'd be talking about something fairly serious here that would cripple Canada in a way that would affect the lives and the security of its people.
The other important thing to remember is that in the example in paragraph 2(a), where you find “the economic or financial stability of Canada”, we are talking about “interference with the capability of the Government of Canada in relation to”... “the economic or financial stability of Canada”. Therefore, it is not just the fact of affecting that particular area, but affecting the capability of the government to maintain economic or financial stability.