Here’s a PNG that will show a different image in Apple Software

This is wild: while writing his own parallel-decodable PNG implementation, David Buchanan discovered he had a bug in his code. Soon after, he found out Apple has the same bug in their implementation which ships. As a result, it’s possible to craft a PNG in such a way that Apple’s decoder will show a different …


This content originally appeared on Bram.us and was authored by Bramus!

This is wild: while writing his own parallel-decodable PNG implementation, David Buchanan discovered he had a bug in his code. Soon after, he found out Apple has the same bug in their implementation which ships.

As a result, it’s possible to craft a PNG in such a way that Apple’s decoder will show a different image. Because Safari delegates the task of decoding images to the OS, all Apple browsers — including MobileSafari — also show the “wrong” image.

If you’re using Apple-flavoured software, you should see “HELLO APPLE”, and on all other software, you should see “HELLO WORLD”.

Here’s a side-by-side comparison:

Chrome (left) vs. Safari (right) showing the Ambiguous PNG

Because Chrome uses its built-in PNG decoder, it is not affected by this.

David also created a tool to craft your own PNG.

PNG Parser Differential →
Ambiguous PNG Packer →


This content originally appeared on Bram.us and was authored by Bramus!


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