Exploit in Pixel phones can undo cropping of screenshots
Google fixed a “very serious” vulnerability related to the markup screenshot tool on Pixel phones with the March security update. Two reverse engineers discovered more details about this vulnerability this weekend. They found that Pixel users are still at risk if they have used this tool. This is what’s going on.
Exploit in markup screenshot tool: the short explanation
You can take and edit PNG screenshots in the screenshot markup tool on Pixel phones. One of those editing options is cropping or cropping the screenshot. Two reverse engineers Simon Aarons and David Buchanan found out that a so-called “aCropalypse” exploit made it possible to undo the cropping of the screenshot.
It could therefore be possible to reappear sensitive information that has been removed from the screenshot via cropping. A criminal can misuse that information and use it to blackmail the victim. For example, have you removed an account number from a bank card via Markup and then shared the screenshot with someone? Then the recipient can undo those edits. In fact, 80% of the screenshot can be recovered, allowing viewing of personal information such as addresses, phone numbers and other private information. If you have shared the edited screenshot on social media, you can run even more risk in some cases.
The two reverse engineers who discovered this explain how it works in this article on their blog.
There is still a risk
According to Buchanan, the exploit has been around for about five years, since the launch of the markup tool in Android 9 Pie in 2018. And therein lies the problem. The March security patch fixes the problem with cropped screenshots through the markup tool, but not some screenshots that Pixel users have cropped and shared with others in the past.
The reverse engineers have built a website, acropalypse.app, where you can find out if a shared screenshot is at risk. Unfortunately, it’s not clear how widespread this problem is among Pixel users. According to Aarons and Buchanan, some websites such as Twitter handle screenshots in such a way that no one can exploit the vulnerability. This does not apply to other platforms. Talking specifically about Discord, Aarons and Buchanan indicate that the platform did not patch the exploit until after the recent January 17 update. It is unclear whether screenshots shared on other social media and chat apps are also at risk. So the risk is still there even after the March security update is installed on the Pixel phone.
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Several serious vulnerabilities in Android have been discovered in recent weeks. Project Zero, Google’s security research team, found a number of major vulnerabilities in Samsung modems last week. This issue made it possible for criminals to remotely penetrate a phone without the user noticing. The modems can be found in these popular Android phones. In addition, there is a major security risk on Android phones that can easily bypass two-step authentication.
Do you use the markup screenshot tool on your Pixel to crop screenshots? Let us know in the comments.
