Firefox (at least on Windows) has a special Flash installer baked into it for several years — if it can't find the plugin, it prompts you with an infobar, which then kicks off a streamlined installer that downloads a xpi package and installs it even without administrative privileges. Theoretically that plugin repository mechanism is crossplatform, and on some Linux platforms it can install a mplayer plugin, but it's purpose-designed for Flash and I'm not sure there are any other plugins for Windows in the repo that Mozilla hosts.
When they first implemented it, they also got a special license from Adobe to distribute the Flash xpi from addons.mozilla.org, and did so happily, but I think the file is hosted by Adobe these days.
When they first implemented it, they also got a special license from Adobe to distribute the Flash xpi from addons.mozilla.org, and did so happily, but I think the file is hosted by Adobe these days.
They've also baked in a special Flash updater too — if your Flash plugin has known security vulnerabilities Firefox will prompt you to automatically update it: http://blog.mozilla.com/metrics/2009/09/16/helping-people-up...