Samsung isn't leaving its flagship of yesteryear completely high and dry in this age of Stagefright vulnerability. An update is being sent to the Verizon Galaxy S4 today that patches the Stagefright vulnerability, and adds a few more fixes for good measure.
The full changelog is available above. As you can see, there's nothing new. There sure are a lot of fixes for a more than two-year-old device. You would think that stuff would be worked out already, but I guess not. The Stagefright fixes are the most important aspect, though. The update is rolling out now and should be on all devices in a few days.