Apple knows. Look at the security content of iOS 7.1.

http://support.apple.com/kb/HT6162

I reported CVE-2013-6835. They fixed Facetime-Audio from Safari, but not from other browsers (yet?). This is quite a wide issue. I do not think letting every individual developer know is feasible. I did it for a few bad issues, but there's a limit to what can be done.

And a lot of these can be found in a matter of minutes anyways.