Discovering a bug that could put people's lives and/or freedom at risk if they don't do something about it makes it okay to go public immediately. That said, by all means notify the maintainer/vendor as well.
It should always be assumed that someone else (if not several someone elses) have already discovered the same flaw and are currently taking advantage of it while users remain totally unaware of their actual risk. By going public immediately, you give as many of those users as possible a chance to protect themselves.
Waiting to disclose something harmful when the users in danger could otherwise take steps to make themselves safe would be like not warning people entering a building not to go in because of a gas leak until after you've contacted the building owner and the fire department has shown up.
> Discovering a bug that could put people's lives and/or freedom at risk if they don't do something about it makes it okay to go public immediately
The flipside of course is ... does your disclosure increase the risk?
> aiting to disclose something harmful when the users in danger could otherwise take steps to make themselves safe would be like not warning people entering a building not to go in because of a gas leak until after you've contacted the building owner and the fire department has shown up
I don't think it's like this at all. The risk of a gas leak is not increased by telling people about it and can't be prevented after its occurred. To stretch your analogy, I'd say its more like you've found the gas leak and instead of turning off the gas supply are instead running around outside the building shouting about how there's a gas leak.
> Expecting people to hold off on disclosure of something harmful
That's not what they said though. They said "please consider notifying the maintainer/vendor before publishing your findings, even if you intend to publish right away" (emphasis mine)