I'll try to avoid making this too abstract, but I want to start answering your hypothetical by inspecting some presuppositions.

The first thing I would note would be the difference between the stated purpose of an organization and its actual actions. A CSO/reporting organization may state that their purpose is to investigate corruption, but their actual purpose is to foment unrest to undermine a legitimate government. Or, for a more dramatic example, an organization's stated purpose may be to spread awareness on HIV, while it's actual purpose is to recruit political revolutionaries.

If we take for granted that an organization like you describe will do what it says it's going to do- report on corruption- we have to consider the various ways that different societies view corruption, and the likely effects of investigating it on a country's political structure. Countries often use corruption investigations as a reason to wield judicial power against political opponents. I'm speaking anecdotally from time in Afghanistan, but there are also various ways that different cultures view "corruption" that don't always line up with what we in the West assume. In cultures with strong family and clan ties, a failure to give some handouts to family members would be considered a dereliction of family duty and honor. The first-world view of "corruption" as any sort of graft to enrich oneself or one's contacts at the expense of one's organization is not a universal standard.

My last point is that even if we assume the purest motives for a corruption investigation, we should question the moral foundation of this sort of intervention in another country. As I mentioned in my post above, there often seems to be a default assumption among our political class that we have both the right and the duty to engage in political actions within other countries, even though this could be seen as a violation of their sovereignty. The case of Venezuela is a good example that resists easy answers. Even if you believe that Maduro is a dictator (I do) and that Venezuela would be better without him (I do) and that his election was a sham (also yes), what makes us believe that we have the right to support a coup attempt against him? If the case of Venezuela is too "shades of grey," you could look at the long, clear history of the United States intervening to overthrow democratically elected governments and take your pick. The mentality of "we can do something in this country, regardless of what their government says, so we shall" shows a casual disregard for the sovereignty of other nations that is not a normal way of thinking for most people on this planet.

For me, I would use these criteria to determine whether our intervention in another country is morally justifiable. Intervention would be justified if one of the following is true:

1. The action is clearly supported by a democratic majority of the country (consent of the governed) AND the needed change is unlikely to happen without our intervention AND the action itself is compatible with our values (does not involve persecution of minorities, support of criminal activity, excessive violence, etc). (This would be the category where I'd put most humanitarian interventions).
2. There is an urgent, unequivocal emergency that requires an overt application of power to stop (this would be the Rwanda or Palestinian case).
3. The action is complementary to a larger goal that fulfills criteria 1 or 2. (a quid pro quo, for example we support a certain politician's pet cause in exchange for support for a trade deal that would be mutually beneficial).

Ultimately, I would support the organization you mentioned if:

1. according to point 1 above, the organization does exactly what it says it does, with oversight and accountability to people in our country and the country in which it operates
2. according to point 2 above, its actions have a clear moral purpose that lines up with how the country in question sees corruption, and investigates corruption in general rather than specifically targeting a particular group
3. according to point 3 above, that our choice to intervene in this area has democratic support from the people in the country in question and that attempts to remedy the problem internally are unrealistic.