This question appears because the application currently running in Adobe Flash Player is trying to access information from a site outside its own domain, using an older system of security.
Flash Player is alerting you that information might be shared between two sites and is asking if you want to allow or deny such access.
In some cases, that person or company might not have indicated which other sites are allowed access.
Therefore, Flash Player alerts you before it tries to access [site2].
Chapter 2 – Flash Player environment: This chapter describes the different environments in which Flash Player runs, where Flash Player files are stored on the system, the processes that Flash Player generates, and information on determining which version of the player is installed on a system.
Chapter 3 – Player installation: The licensed installers for Flash Player are available in a number of forms.
To access the local Flash Player Settings Manager that is native to your operating system: Adobe is committed to providing you with options to control SWF or FLV content and applications that run in Adobe Flash Player.
To see if the Flash plugin is working and what version is being used, visit one of these pages: If Flash is not installed, this may trigger the Plug-in Finder Service, which you can use to download and install the Flash plugin on Windows (see below).
At time of writing, the Plug-in Finder Service is triggered but fails to install the Flash plugin on Linux or Mac OS in Firefox 3 and above (you will need to manually download and install the plugin).
Distribution licenses are free of charge and can be acquired through the online licensing application.
For answers to a number of questions regarding Flash Player licensing and deployment, see the Adobe Player Distribution FAQ.