I'm attaching the corrected version. Here is how it was done (no plugins, just plain PhotoShop):
Rotate canvas 0.33 degrees CCW (correct for the fact that the camera was not perfectly leveled).
Free transform. Move the bottom-right corner up by 4px, top-right corner down by 2 px (correct for the fact that the lens axis was not perpendicular to the stairs). These pixel measurements refer to the large image posted on photo.net. For the original multi-megapixel version you'll have to move corners by a couple of dozens pixels.
Increase canvas size by 150% (otherwise the Spherize filter we will apply will afect image margins).
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I'm attaching the corrected version. Here is how it was done (no plugins, just plain PhotoShop):
Hope that helps.