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Defective CSS code crashes, causes iPhones to restart

Apple iPhone X flagship, iPhones plagued by a CSS bug (Source: Apple)
Apple iPhone X (Source: Apple)
Using the rather new backdrop-filter CSS property can lead to a crash of the entire iOS on an iPhone. An exploit that does this and the code behind it have recently been unveiled by a software engineer and security researcher at Wire. The even worse part is that this issue might affect macOS-driven systems as well.

Those trigger-happy haters who usually blame Apple for all the possible fails of the iPhones and Macs should hold their horses because today's problem is not the fault of the tech giant based in Cupertino. However, the bug that has just been discovered in Safari that allows a CSS/HTML attack to crash the browser and restart iPhones (and probably iPads as well) seems serious enough for Apple to do its best and patch it as soon as possible.

Sabri Haddouche is a software engineer and security researcher who works at Wire (the instant messaging app, not the website) and he did more than just discover this bug. He came up with a proof-of-concept piece of code that shows clearly how is this done. For more details, you should check out this Twitter post.

To make a long story short, CSS code that uses the backdrop-filter property is used to blur or color shift the area behind an element. However, this task is quite intensive on a mobile device/operating system, so the iOS graphics processing library crashes, leading to a restart of the phone itself. In macOS, the CSS/HTML attack only slows down the browser. However, by adding Javascript into the equation, Haddouche managed to brick macOS. 

Apple was already notified about this issue and is currently investigating it. We will get back to this issue as soon as Apple patches it, so stay tuned.


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Codrut Nistor, 2018-09-17 (Update: 2018-09-17)