AI Summary: Ambiguous PNG Packer is a tool designed to create PNG files that display differently when viewed in Apple software versus non-Apple software. Its primary use case is to demonstrate the manipulation of image rendering based on the viewer’s platform, showcasing unique features such as the ability to produce different images through refreshes, highlighting potential vulnerabilities in Apple’s image handling mechanisms.

README

Ambiguous PNG Packer

Craft PNG files that appear completely different in Apple software

For context: https://www.da.vidbuchanan.co.uk/widgets/pngdiff/

UPDATE: Apple seems to have patched this now, I’m not sure in which version exactly

Sample output:

If you’re viewing this via Apple software (e.g. Safari) you should see an image of a mac, and on other non-Apple software, you should see an IBM PC. (Note: If you’re in Safari and still seeing the IBM PC, hit refresh a few times…)

As a bonus, here’s a race condition I found in desktop macOS Safari:

You should see a slightly different image on each page refresh!

Here’s a “live” version, which self-refreshes on each frame: https://www.da.vidbuchanan.co.uk/widgets/pngdiff/race.html