Side-channel attacking browsers through CSS3 features. Really clever attack. Sites like Facebook offer iframe widgets which show the user’s name, but due to the cross-origin resource policy cannot be introspected by the site on which they are embedded. By using CSS3 blend modes it’s possible to construct a timing attack where a stack of divs layered over the top of the iframe can be used to derive the embedded content, by taking advantage of blend modes that take different amounts of time depending on the colour of the underlying pixel. Patched in Firefox 60 and Chrome 63.
Recent articles
- Phoenix.new is Fly's entry into the prompt-driven app development space - 23rd June 2025
- Trying out the new Gemini 2.5 model family - 17th June 2025
- The lethal trifecta for AI agents: private data, untrusted content, and external communication - 16th June 2025