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Google Pixel bug lets you “uncrop” the last four years of screenshots
New tool reveals cropped-out screenshot info isn't deleted, can be recovered.Back in 2018, Pixel phones gained a built-in screenshot editor called "Markup" with the release of Android 9.0 Pie. The tool pops up whenever you take a screenshot, and tapping the app's pen icon gives you access to tools like crop and a few colored drawing pens. That's very handy assuming Google's Markup tool actually does what it says, but a new vulnerability points out the edits made by this tool weren't actually destructive! It's possible to uncrop or unredact Pixel screenshots taken during the past four years.
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the Android 9 release of the Markup tool worked correctly and truncated the overwritten file. Android 10 brought a lot of dramatic "Scoped Storage" changes to how file storage worked in Android, though. It's unclear how or why this happened, but perhaps as part of that huge wave of file-handling commits, one undocumented change made it into the Android Framework file parser: the Framework's "write" mode stopped truncating overwritten files, and the bug in Markup was created. The Markup tool relied on the OS's file handling, and the way it worked changed in a later release, which it looks like nobody noticed.
Most phones have a similar functionality, where you take a screenshot and can tap a little thumbnail of it that sits on screen for a second to bring up the editor/sharing options. This bug is specific to the "Markup" tool that Google Pixel phones have though, but it's possible other tools baked into custom Android UIs might suffer from it as well.
I checked the images output by the screenshot editor on my phone, which isn't Markup since it's not a Pixel phone, and the file doesn't contain any of the redacted data.