This question is an exact duplicate of:
It looks like there's been a recent change in the profile picture system. However, that appears to have broken images which are not squares.
This is what I see on my profile page. It's horizontally stretched, and it looks quite ugly:
For comparison, here's the top bar, which looks fine.
I've seen other peoples' pictures which are stretched vertically presumably their pictures have landscape-oriented originals, while mine is in a portrait configuration.
I'm on Chrome 71.0.3578.98 for Windows 10.