Honestly I think full disclosure with a courtesy heads-up to the project maintainers/company is the most ethical strategy for everyone involved. “I found a thing. I will disclose it on Monday. No hard feelings.” With ridiculous 45-90 day windows it’s the users that take on most all the risk, and in many ways that’s just as if not more unethical than some script kids catching wind before a patch is out. Every deployment of software is different and downstream consumers should be able to make an immediate call as to how to handle vulns that pop up.