> I want to understand how it leaked. I guess a whole lot of people were looped in between September 21 and October 21?

Yes. I was at AWS when Spectre and Meltdown were discovered, and we received approximately a month of advance notice and put together teams to apply mitigations. The work of the team was on a need-to-know basis--even team members' managers only knew they were pulled onto a critical project, not what the specific project was. But there were still 30+ people in the company who knew, and that was just one company (I'm guessing Google/Azure/other cloud providers got similar advance notice).

Now, this is a much wider scale vulnerability, in the sense that Spectre/Meltdown primarily impacted cloud providers, but this attack impacts literally anyone who runs PHP. Dozens, if not hundreds, of companies likely got advance notice that a patch needed to be installed. In those companies there are teams of people applying those patches. All it takes is one of them who wants 15 minutes of internet fame to leak the details.

Even some smaller vulnerabilities are spread through hosting companies pretty quickly within a day or two prior to public release, to give teams time to make sure staff will be ready to patch immediately.

The wider the pre-release news spreads, the more chance you get someone who will spill the beans (intentionally or not).