client/my-sites/plugins/controller.js
function getCategoryForPluginsBrowser( context ) {
	if ( context.params.plugin && includes( allowedCategoryNames, context.params.plugin ) ) {
		return context.params.plugin;
	}

	return context.params.category;
}
function getCategoryForPluginsBrowser( context ) {
	if ( context.params.plugin && includes( allowedCategoryNames, context.params.plugin ) ) {
		return context.params.plugin;
	}

	return context.params.category;
}
The plugin browser can be rendered by the `/plugins/:plugin/:site_id?` route. In that case, the `:plugin` param is actually the side ID or category.