Why wouldn't you want to update your Plugins?
You are like 3 versions behind with Flash and 10 versions behind with Java.

Type about:config in the URL bar and hit Enter.
If you see the warning, you can confirm that you want to access that page.

Pref = plugins.update.notifyUser if it shows as True, double-click that pref to toggle it to False

I still have this problem, and the plugins.update.notifyUser is set to false and the page keeps appearing. The main plugin that won't update is Microsoft DRM

The "MetaStream 3 Plugin r4" extension has been reported to cause this issue with the plugin check page appearing.

• /questions/832793

You do have a very old Shockwave Flash 10.0 r32 plugin installed

Your above posted system details show outdated plugin(s) with known security and stability risks that you should update.

1. Shockwave Flash 10.0 r32
2. Next Generation Java Plug-in 1.6.0_17 for Mozilla browsers