It seems Firefox has some kind of trouble updating the Adobe Flash plugin and it keeps telling me it is unsafe.
yum update won’t help.
Here is how to fix it (in my case):
A. Quit Firefox
B. login through SSH, and delete plugin.dat:
rm -f $HOME/.mozilla/firefox/*.default/pluginreg.dat
C. Start Firefox and go to: Tools > Add-ons > Plug-ins
There you will now see: Shockwave Flash 188.8.131.522
And you’re fixed. (as that is the newest at March 5th 2015)