Imgur seems to believe that this image is 18+ (though it appears to not be).

Done.

A CSS script could do that... if the :has() selector is supported.

With that said, I've recently run into issues with that selector not being supported (due to it being recent CSS spec) in two different (but not recently updated) user style extensions that I've tried it with (in one, it is entirely unrecognized; in the other, you get errors when trying to do nontrivial things in the :has() ).

I could copy/paste some example user CSS for you if you'd like to see if you can get it working.

@Wander A more quality (but more labor intensive) solution would be to have an account setting that toggles a short CSS file containing overriding CSS for the adult image blur. This way, users could choose to have or not have that blur regardless of which theme they chose (without having to have two separate copies of each main CSS theme to achieve that).