Increasing local contrast while reducing overall contrast when working with an image that has very high contrast between adjacent areas will cause such a glow in the lighter areas that are nearest to the darkest areas. Many apps use such a method and can, if applied strongly enough, result in the halo effect.

The photo above was processed from a single RAW file using the HDR Tool in Canon's Digital Photo Professional. The same photo after RAW conversion without using the HDR tool is below. Notice that even after reducing contrast, pulling down the highlights, and boosting the shadows the bright sky has lost a lot of detail, yet the shadows are still quite murky. When local contrast is increased to recover detail in both the highlights and the shadows, the halo around the boundary between the dark and light parts of the image appears.

In the example posted in the question, the light is fairly harsh and on the other side of the subjects from the camera. One would expect the ladies to be little more than silhouettes when the photo is exposed for the brightest areas of the photo.