Hi Jeff
The security issue is regarding all Joomla versions prior to 3.4.6 (
https://blog.sucuri.net/2015/12/remote-command-execution-vulnerability-in-joomla.html). This object injection vulnerability makes your sites very easy to compromise. To save you some heartache in the future I would strongly suggest updating all your Joomla sites. It is a widely known vulnerability and very easy to implement with a number of instances already been brought to our attention among Joomla51 users.
Regardless to amend your issue try adding the following to the Custom CSS field of your templates parameters....
@media only screen and (max-width: 767px) {
.wrapper960 {
width:100% !important;
}}
Ciarán