Would you code in an extra check?
https://www.dropbox.com/s/ycg92nwn22...l150.png?raw=1 does not tecnically end in ".png" and this is not currently accepted, but is a great way to host images
A fast hack could be, besides checking if file ends in
- .jpg
- .gif
- .png
also check if ends in
- .jpg?raw=1
- .gif?raw=1
- .png?raw=1