As detailed in a thread Aaarons posted on Twitter, the aptly-named “aCropalypse” flaw makes it possible for someone to partially recover PNG screenshots edited in Markup. Once Aarons downloads the image and exploits the aCropalypse vulnerability, the top part of the image becomes corrupted, but he can still see the pieces that were edited out in Markup, including the credit card number. You can read more about the technical details of the flaw in Buchanan’s blog post