Aside from looking at the file size, you can check any PNG image with pngcheck [1]:

     pngcheck good.png
    OK: good.png (467x389, 32-bit RGB+alpha, non-interlaced, 88.2%).

Compared to a vulnerable image:

     pngcheck bad.png
    bad.png  additional data after IEND chunk
    ERROR: bad.png

macOS Preview, Quick Look, and CleanShot X are safe.

[1] https://www.libpng.org/pub/png/apps/pngcheck.html, available in Homebrew