Who says Adobe doesn't care? They responded to complaints it wasn't going back to 5.x (either clarifying a bad communication or fixing a mistake - not sure). But how much should they expend to guard against something that hasn't actually happened to software that is more than 2.5 releases old?
If there was a huge rush of actual problems, maybe there would be more cause for action. At the moment, though, there's a proof of concept and nothing else. The kind of places that are likely (and I use the word loosely) to open an image from an unidentified source bcause of a *need* to do so, are far more likely to be on 5+. Individual users who are using older versions are very unlikely to *need* to open images from unknown sources *with* Photoshop (as opposed to a simple image viewer).