Can't I just flip this around on you and say you have an ethical obligation to spend some of your time looking for vulnerabilities? If you started looking, you'd find some. Why do you get to free-ride on my work by refusing to scrutinize the stuff you run?
To some small extent, yes, though how much work is up for debate. Maintainer's email and PGP public key is right there on the website? Yeah, I think you're obligated. No email you can find, no way to contact them, or are just outright hostile? No, I think you shouldn't have to deal with that.
But I feel like you agree with that, though maybe not in those exact words. After all, you've had to jump through all kinds of hoops to disclose vulnerabilities, been threatened with lawsuits for doing the right thing, and yet you still practice responsible disclosure in almost every case in spite of the burden of effort and potential risk. Aren't you doing it because you think disclosure is the right think to do? That's all I mean by obligation.
EDIT: sorry, not "responsible disclosure," "cooperative disclosure" or whatever term you want to use for disclosing the vulnerability to the maintainer.
Nobody has to enter a burning car and risk his life but at least you have to call the emergency service or do whatever you can reasonably do to help. And it really doesn't matter whether you are doing your work delivering packages, whether the accident was the fault of the driver because he was driving intoxicated, if somebody else could also help or whatnot.
Discovering a vulnerability is of cause different in most respects - the danger is less imminent, the vendor may have a larger responsibility and so on. But the basic structure is the same - more or less by accident you end up in a situation where there is a danger and you are in the position to help to make the outcome probably better.
So I think one can not simply dismiss that there might be a moral obligation to disclose a vulnerability to the vendor on just the structure of the situation, one has to either argue that there is also no moral obligation in the accident scenario or argue that the details are sufficiently different that a different action - or no action in this specific case - is the morally correct or at least an morally acceptable action.
I would feel a moral obligation to help mitigate concrete physical harm to victims of an accident. I feel no such obligation to protect against hypothetical threats to computer systems.
Chances are, you recognize similar distinctions; for instance, I doubt you feel obligated to intervene in accidents that pose only minor personal property risks.
But I need to be careful saying things like that, because it is very easy for me to say that, because I don't spend any time looking for those kinds of flaws. Security research is pretty specialized now, and I don't do spare-time Windows work. I might feel differently if I did.
I would not judge the (many) researchers who would not necessarily disclose that flaw immediately.
So, it won't be fixed.
Hopefully only one or two people know about the same flaw you found...
Oh, but you would know ahead of time if concrete physical harm could possibly come to the victim of an accident?
Well good for you! You should probably be in charge of defending all infosec research, since apparently you can't be hacked.
You said (and I quote):
Can't I just flip this around on you and say
you have an ethical obligation to spend some
of your time looking for vulnerabilities?
No. No, you can't. Unless you could convince me that my Dwarf Fortress skills have a similar magnitude of real-world affect as the vulnerabilities I've discovered on my own and decided to pocket for one reason or another.The ethical conundrums are unavoidable, and those calculations are indeed difficult.
The legal consequences are artifice, and by agreeing to those (while ignoring externalities and not going public), you are likely putting others at risk.