Are you sure that that's the actual source? It seems to be suffering from compression artefacts slightly, and what might have been a somewhat overenthusiastic (i.e. sharp) downscaling.
True but to some extent those problems could be alleviated if you could get to the actual source, which wouldn't have either of the problems I mentioned. Assuming I diagnosed things correctly, which is a bit tricky. The image has definitely been processed though, as evidenced by the ringing.
The only change I did to it was removing a sewer drain in front of the car in photoshop(hence why it's called wallpaper fix) - I haven't done anything else to the photo. Here's the original original file, uploaded right now from my phone:
Apparently I can't access that file but I'll believe you. Although if the original was jpg as well then it was somewhat unfortunate to save it as jpg again as that would result in additional compression artefacts (lossless jpg exists, but isn't exactly common).
That said it's hard to tell whether it's compression artefacts or some 'smart' sharpening that's responsible for the artefacts. It would need to have been compressed pretty heavily to fit in just 4MB.
