>muh root installer
Lol no, this shit is possible even in user level installers. In Unixland, Chrome and Firefox data are generally on your home directory, completely unprotected of reads by default from any program running as "you" or, depending on the distro, and by default, ANY program in the system. In Windows this is not much better, as they are inside %APPDATA% amd suffer from the same limitations. I repeat: stealing all your passwords is as easy as copying this folder, and considering all programs you run have the same permissions as your user, all programs are free to interact with each other's config files. The only sane way out is sandboxing, which Android does by default; any other operating system would require third party sandboxing software (ie. Firejail, Sandboxy), or a complete redesign of the way program storage or even processes altogether are handled, but forget about this ever happening because it would be "bloat" for suckless idiots and could probably require work by distro maintainers' part, which is quite hard considering some distroes, like Debian or Arch, have sloths for maintainers.
Remember: even trustworthy software can become untrustworthy due to the funny way C and C++ (protip: 90% of your system is written with those) handle stuff. Without proper hardening features, and even then, ANY program could steal all of your data if not sandboxed. Desktop security is fundamentally borked and you need to heavily reconfigure your stuff if you remotely want to stay safe.