I don't know how to word this so I'll say it bluntly (and probably bear the blunt of this community as a consequence): If you're a developer of a project that is used in a security-sensitive context, you either be receptive to security concerns or you clearly label your project as a toy project. No one expects you to write perfect code, but we do expect you to fix flaws when you learn about them. Of course, you could…
If actix-web was this important, it should have been adopted by the community before now. Maybe languages need a way of setting the expectation to that if your library becomes essential to the community (and if licensing allows) the core developers are going to fork it and find a way to govern/maintain it the same way they maintain the rest of the project.
I think about this a lot with Racket lately. Some of the core packages that everyone uses for date/time, Markdown parsing, etc., were written by a single guy in his spare time, who a few months ago was making noises about quitting the language (so far so good though).