In the question shown above, [site1] represents the name of the person or company who created the application that is trying to access another site, represented by [site2].
The site being accessed, [site2], determines which other sites can access it.
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.
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.
If you see this question and are concerned, you can contact the person or company being accessed and notify them that you are seeing this question.
Note that it is the person or company that has created the application you are using that is requesting such access, not Adobe (unless Adobe has created the application that wants access to the other site).