Updating to 6.5 changes security settings to "Low" without notification
I updated from 6.0.7 to 6.5 today, and I had the security levels to High, and after the update they where set to Low without any type of notification, enabling JS which I had disabled in High.
I guess it's related to "Bug 20264: Change security slider to 3 options".
Most users won't realize that their security settings have been lowered.
Trac:
Username: ggavilan