Visit Adobe's website for information on security and stability issues affecting Adobe Flash.Adobe Flash (formerly Macromedia Flash), refers to the Flash Player and browser plugin needed to handle SWF videos, web page animations and interactive content. An uninstaller can be downloaded from to remove Flash from Mac or Windows systems.
To install Flash or to update to the latest version for your operating system, visit the Adobe Flash Player Download Center (see the system requirements and FAQ pages for more information).
Flash 9.0.r28 and earlier versions of the Flash plugin installer copied these two files to the installation directory of Firefox and other detected Mozilla browsers: You would then have needed to copy these two files to the plugins folder of undetected browsers (e.g., zip builds).
Note that an XPI package that was available for Flash 9.0.r28 and earlier using the "Install" link at Plugin Doc also copied the Flash plugin files to the Windows System directory's Macromed\Flash folder and added a registry entry so that all Mozilla browsers could find the files through plugin scanning, using a Windows registry PLID scan  Starting with Flash 9.0.r45 the Flash plugin installer for Firefox and other Mozilla-based browsers does not copy any files to the browser plugins folder.
See this blogspot article for details, including a screenshot.
Starting with Flash Player 11.2 on Windows, an option for silent, automatic updates is selected by default when you install Flash.
Instead, the files "NPSWF32.dll", "flashplayer.xpt" and related files are placed in the Macromed\Flash folder located in the Windows System directory (e.g., C:\WINDOWS\SYSTEM32\Macromed\Flash) and the installer removes any copies found in the installation directory of detected browsers.