You do know that Chrome, Firefox, and Edge (at least) have all stated that they will drop support for flash as soon as it's EOL'd. So why again would open sourcing Flash after that point make a difference in your security?

Only thing you can argue is that if someone is using old out of date software they would be at risk, but they are already at risk. Open sourcing Flash would not make it any less secure if it's not being used anywhere anymore.

Do you suppose that nobody will use the open-source version of Flash to make a spin of Chromium with Flash support, to serve the very kind of people who just can't seem to live without their legacy apps? If the browsers are open source and Flash is open source, millions of systems will be left vulnerable in this way.

So you don't want some code to be open source because you care about some tech people may used that open source code and get infected? Java was open sourced and you don't have an open source Java plugin forced upon you.

Yes, I do, quite often.

What do you mean is Firefox and Chrome forcing Java on you? Did Java getting open sourced affected you in a negative way? how?

What is preventing them bundling the old out of date Flash with Chromium?

Why even bother worrying about Chromium? People who are going to want the legacy Flash stuff are running Windows and there isn't even Windows build of Chromium. How come people on HN always come up with some ridiculous edge case that has zero baring on reality.