I reckon it’s time for distressed type to make a comeback—CSS is ready for it.
First of all, don’t panic—this browser vulnerability has been fixed, so the headline is completely out of proportion to the reality. But my goodness, this was a clever technique!
The technique relies on luring users to a malicious site where the attacker embeds iframes to other sites. In their example, the two embedded iframes for one of Facebook’s social widgets, but other sites are also susceptible to this issue.
The attack consists of overlaying a huge stack of DIV layers with different blend modes on top of the iframe. These layers are all 1x1 pixel-sized, meaning they cover just one pixel of the iframe.
Habalov and Weißer say that depending on the time needed to render the entire stack of DIVs, an attacker can determine the color of that pixel shown on the user’s screen.
The researchers say that by gradually moving this DIV “scan” stack across the iframe, “it is possible to determine the iframe’s content.”
On Ev’s blog, Marcin goes into great detail on theming an interface using CSS custom properties, SVG, HSL, and a smattering of CSS filters.
I was kind of amazed that all of this could happen via CSS and CSS alone: the colours, the transitions, the vectors, and even the images.
Oh, how I wish I could’ve been at Web Directions Code in Melbourne to see this amazing presentation by Charlotte. I can’t quite get over how many amazing knowledge bombs she managed to drop in just 20 minutes!
This use-case for blend modes is making me thirsty.
Also: look who’s blogging again!