Update:Apparently SP3 doesn’t downgrade the player. It’ll only install an older version 9.0.115 if you don’t have the latest 9.0.124 already installed, according to this blog post from Ryan Stewart. More info here.
The latest Windows XP service pack 3 comes bundled with the old 18.104.22.168 version of the Flash player. This version, beside not being able to play back some of the latest web content, has some major security flaw, along with a weaker security model and some other bugs.
If you apply this update to your windows system, make sure you install the latest Flash player from here.