Given the frequent updates and security vulnerabilities with Adobe Flash Player, I would always recommend running the latest version of Flash Player. However, there is the rare instance where you need to test something out. Such was the case recently with a client. A web-based application that they use for monitoring had stopped working recently and one of the applications that had updated since it was last known to be working was Adobe Flash Player.
They were running the latest version of Adobe Flash Player 18.0 and wanted to try uninstalling the ActiveX version of Flash Player to install an older version. Note that this was on Windows 7, which does not have Flash Player bundled with Windows Updates as in Windows 8+.
When trying to run the older version installer, you are greeted with an error that states:
The installation encountered errors:The version of Adobe Flash Player that you are trying to install is not the most current version. Please visit the Player Download Center to obtain the latest, most secure version.
The old Flash Player installer somehow knew that there is a newer version available, so it aborts the install. This happened after uninstalling Flash Player ActiveX, so there must have been something left behind. I went ahead and uninstalled the Flash Player NPAPI version as well to make it easier to identify the remnants. Sure enough, I found a location in the Registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\FlashPlayer\SafeVersions
And, for 64-bit Windows, you also have this location:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Macromedia\FlashPlayer\SafeVersions
Once Flash Player was uninstalled the SafeVersions key was the only location with values under Macromedia. You can see the older versions denoted with (hexadecimal) all F’s to denote that they are not allowed to install. On the client’s computer, the versions up to 18.0 were listed and version 18.0 had a different data for its value, seemingly denoting it as the current version.
Once I deleted the Macromedia key from the registry, the older installer was able to proceed. I have not tested it but supposedly if you use the official Flash Player Uninstaller, it will automatically remove the SafeVersions key. Once you have that key deleted, the next step is to install the older version, which you can find previous version installers on Adobe’s Archived Flash Player version page. I only recommend running off an old version of Flash Player for testing purposes and then getting back up to the current version before returning to regular use.
By the way, the client’s problem was not a new version of Flash Player. It ended up being something with their account settings not being able to access the server where the data is pulled from and displayed in Flash-generated charts. Flash Player updated them to the current version again and with their account corrected, they were able to see the web app just like their co-workers.